What is the Stanford Bunny? http://en.wikipedia.org/wiki/Stanford_bunny This model is derived from user Phooky's flatfoot version. This also is not a simple decimate, it was planar angle-limited, then triangulated, then decimated slightly to achieve the desired look. This model also has Z-Axis position zero on all the base vertices, so it should print flat. I updated the model with a few extra faces, to help with printing some of the more angular surfaces.I usually print the regular Stanford Bunny as a test print. Cura seems to slice it better than Slic3r, at least according to similar prints I've done using each. Drooping on the bottom of the ears is common and usually means your cooling fan isn't directing enough air at the extruding PLA. Lower PLA temperatures and thinner layer heights should help drooping as well. For printing on a Printrbot Simple Metal 1403 Printer, http://www.thingiverse.com/thing:356001 is the fan shroud that helps prevent drooping significantly. Similar designs may be available for other 3D printer configurations. Gaps in the top layers of the model can mean your extrusion steps are wrong and you'll need to calibrate the M92 E Value in your printer. There are instructions on how to do this online.