Major new features:

• Honeycomb (hexagonal) infill pattern!
• SVG export for DLP printers and other purposes
• automatic arrangement for printing multiple copies of the same object (thanks Triffid Hunter for contributing this one)

New features:

• new Reslice command in the File menu
• customizable G-code to be executed at layer change

Improvements:

• huge speed boost (20%-50%) and more parallelization of long-running algorithms
• new implementation of support material generation
• don't slow down travel moves when cooling is enabled
• new --threads command line option to set number of parallel jobs

Minor improvements:

• enable G0 automatically for Mach3
• allow decimal values for skirt/duplicate distances and speeds
• added the coordinates of the first non-manifold edge to the warning messages
• only output M109 if there's none in the user-supplied start G-code
• make sure all concentric fill loops are extruded in the same direction to prevent sudden changes of direction

Changes:

• --duplicate-x and --duplicate-y were merged into a single --duplicate-grid option

Bugfixes:

• some holes were filled
• the No Extrusion mode had no effect
• use M109 for bed control (Makerbot)
• use P instead of S for M106 (Mach3)
• fixed some fatal errors

• new fan always on option
• bed temperature control (first layer/other layers)
• Growl notifications

Improvements:

• some algorithms are now less complex (thus faster with larger models)
• fill/perimeter contact is maximized for line pattern
• slowdown is now triggered regardless of whether a fan is used
• allow to use config options in start/end G-code, like for output filename pattern
• throw an error if a user wants to print a 0mm layer
• remove M82/M83 codes for Makerbot output

Changes:

• the Use relative E option is now back in the GUI
• remove G0 from the GUI until most firmwares implement it
• avoid G92 codes for Mach3 output

Bugfixes:

• retraction wasn't triggered when moving between copies
• a bad "bridge fan end" string was sometimes inserted in G-code
• fixed some fatal errors
• fixed some bogus non-manifold errors happening with certain values of first layer height
• infill extrudates were escaping perimeters sometimes

• a new rock-solid slicing algorithm, based on a topological approach, able to process efficiently a wide range of STL files without any warning
• generation of support material (optionally, with a second extruder)
• cooling and fan control
• ability to read the AMF format

New features:

• first layer temperature
• support for Makerbot and Mach3 G-code flavors
• duplication is performed on generated toolpaths instead of 3D mesh, resulting in a nearly-constant time for any number of object copies
• infill and support material are multi-threaded, so they will take advantage of multiple CPUs/cores
• support for custom post-processing scripts
• new notes field in configuration profiles

Improvements:

• uses 40% less memory
• ability to load multiple config files using the command line
• ask for confirmation when slicing more than one copy
• contours and holes are extruded in the same direction (ccw)
• skein multiple files with a single command from command line
• some compensation for hole shrinkage

Minor improvements:

• do not display the progress dialog as an application-wide modal dialog
• Config files are now portable between Unix and Windows and allow for Unicode characters
• added extrusion multiplier to G-code comments

Bugfixes:

• models with rounded walls had small useless infill regions
• small perimeter speed was applied to all holes too, regardless of their size
• fixed some fatal errors

• thin walls!
• new Output Filename Format option to allow for complex output filenames using option values (like foo_3perimeters_0.15height.gcode)
• automatic retraction at the end of the print

Improvements:

• much better overlap between infill and perimeters in those situations where previous version was still producing gaps
• smarter order for hole perimeters to save travel and time
• large internal refactoring (less memory and some speed)
• bridges now have higher priority than other solid regions
• loops are now closed better
• use solid print speed for internal solid layers too
• checkbox in GUI to enable comments in G-code
• warn if no layers were detected

Changes:

• Windows package is now distributed as a ZIP file rather than a self-extracting executable

Bugfixes:

• some island having no holes and contained in holes themselves were ignored
• fatal error in arc detection code
• wrong month number in output
• small regions were infilled even with fill_density = 0
• fill was escaping perimeters near some corners
• other fatal errors removed, especially when dealing with dirty files

A Slic3r forum was created in the official RepRap forums. Also, about 50 people sit in the FreeNode IRC #slic3r channel.

Some notable things appeared in the web recently. Neil Underwood (well known as Spacexula) posted pictures and a video of a print he did on the official RepRap blog. The first outstanding thing is that he reached a 0.01mm layer height. The second outstanding thing is that he used Slic3r!

Richard H. (well known as Richrap) is posting a multipart illustrated Slic3r guide to his colorful blog. It's a very good work, so thank you Rich!

Michael Andresen (well known as blddk) posted some screenshots to show differences between the various fill patterns available in Slic3r. Don't miss the interesting article Gary Hodgson posted about new possible fill patterns.

Pointedstick (Nathaniel Graham) posted two good blog articles about high-resolution printing, in which he talks about using Slic3r: this and that.

Brazen Artifice posted a couple articles about retraction and preloading last settings.

Sparr posted a picture of an object he printed with and without enabling the native arcs support in Slic3r.

The good Kliment Yanev added an option to customize the slicing command in his excellent Pronterface, to allow for easy integration with Slic3r. (See the Slic3r README for guidance.)

• Slice and save as... command to choose the output file name
• Compatibility with Windows XP 64
• Total filament length is written to the output file and showed on command line

Improvements:

• Improved flow and overlapping for solid surfaces by using a better physical model in internal calculations; this gives much higher quality making it less sparse then it was before
• Improved the slicing algorithm; this should reduce the STL warnings
• Better overlapping for loops
• Concentric infill now uses the adjusted flow spacing for better surface quality; it also starts infilling always from the center point.
• Reduced packages size by 10-20%; they also launch faster
• Always use rectilinear infill for internal solid surfaces
• Limit skirt height to print height

Bugfixes:

• Concentric infill was throwing errors
• Extrusion was calculated incorrectly for clock-wise arcs when using the experimental --gcode-arcs option

• New extrusion math for more accuracy
• Make sure there are no empty layers at the bottom
• Don't slow down retractions on bottom layer
• Remember last opened directory (until application is closed)
• Don't die when config has unknown options
• More STL files are now accepted

Changes:

• Default infill angle is now 45°
• Default retraction speed is now 30mm/s
• Comments in gcode must now be explicitely enabled with the new --gcode-comments option

Bugfixes:

• Objects had slight dimension errors
• Removed fatal errors thrown during infill (small regions and infill every N layers)
• Fixed bolding and font issues on Windows
• Removed fatal error when nothing in a single layer could be parsed
• Duplicate was giving bad number of copies

• optimal bridging direction is detected for more bridges
• flow width is auto adjusted to avoid leaving gaps at the border of solid regions
• customizable speed for small perimeters
• customizable multiplier for the flow rate used when bridging

Improvements:

• important settings are marked in bold -- new users can start printing by changing only those ones
• infill segments are now connected to allow better sticking to the perimeters

Bugfixes:

• 0.5.4 was less tolerant than 0.5.3 about dirty STL models

• distinct speeds for perimeters, infill, solid infill and bridges
• warn about non-manifold or dirty models
• allow solid fill layers to be zero
• new --extrusion-axis option

Improvements:

• high tolerance for dirty models; it will attempt to repair any missing layer (all Prusa Mendel parts now slice correctly!)
• options on command line now override loaded config file
• note used settings in exported gcode

Changes:

• all feed rate options were renamed using the word speed

Bugfixes:

• concentric infill threw errors
• plate was lifted erroneously at Z change
• fill density = 0 prevented generation of extra solid layers
• some bridges, when very close to other solid surfaces, could lead to overlapping infill
• the extrusion width ratio setting produced wrong flow rate sometimes
• removed sparse errors
• could not read back a config file with empty start or end gcode