Slic3r 0.7.1 versus 0.9.8

The precompiled Pronterface I am using comes with Slic3r version 0.7.1. The current version  of Slic3r as I write this text is 0.9.8. Slic3r is the tool you need to convert a digital 3D model into printing instructions for your 3D printer. It cuts the model into horizontal slices (layers), generates toolpaths to fill them and calculates the amount of material to be extruded.  An  issue with the printed result made me decide to try the new version. 

Part left Slic3r 0.7.1, part right Slic3r 0.9.8

The left part in the picture is sliced with Slic3r 0.7.1 and the right part is sliced with Slic3r 0.9.8. The difference is that the left part has hollow walls. The hollow walls made me decide to try the new version. Note that the hollow walls are not part of the design! You can check out the design yourself at: http://www.thingiverse.com/thing:20830. As you can see on the right, this issue is fixed in the latest version. Another improvement, Coen pointed me at, is that the printed surface is smoother.

Part left Slic3r 0.7.1, part right Slic3r 0.9.8

When you look closely at the left part in the image above, you notice a line from top to bottom. It marks the place where the printer head made a step to the next Z-level (height). The part on the right does not have this line.