I'm liking slic3r a lot. The speed improvement over SF is amazing, seemed like something must have gone wrong
One thing i find myself doing quite often and should be fairly easy to add to slic3r, is changing speeds partway through the print.
I've been doing this just by merging gcode generated for 2 different speeds. This helps on things with long peninsulas in the lower layers, so you can go real slow to get them some strength before beating them up at higher speeds.
Just a thought, keep up the good work this is great stuff.