Slic3r seems to have this printing strategy where it will alternate printing details on each side of a print. i can only assume why (cooling?). this back-fires when using print materials that ooze a lot like nylon and LAYWOO-D3. the side to side tool motion drags thin threads of ooze back and forth across the print, sandwiching them between layers and making the part hard to clean post-print. KISSlicer does a better job with these materials as it prints "in a line" with little tool side to side motion. no, retraction of any amount does not work with these materials (tried it). it would be nice to have some options that affect the "print strategy" and allow the user to select the nature of the way the printing progresses. using more sophisticated moves for materials that can handle it and more continuous movements for those that can not. even just a numeric value from 0-10 that allows one to "dial in" this. for example 0 would print more like KISSlicer and 10 would move provide more tool movements across the print optimizing cooling etc.
I can confirm there's no alternation strategy. Work is oriented towards reducing the number of travel moves and retractions.
Generally Slic3r works. try printing a nautilus gear from http://www.thingiverse.com/thing:27233 with SLic3r vs KISSlicer. wouldn't it be nice if Slic3r could print everything great? I'd think so. I'd like it to be so.