I just tried using support on one of my "basket case" models, and have some reactions:
1) Rectilinear support created a comb like structure, with none of the teeth of the comb supported by anything except their connection to the print bed. The drawbacks to this are:
a) The "Teeth" of the comb were entirely unsupported, which resulted in some of them being knocked over by the print head.
b) The filament was retracted and replaced at the end of each "Tooth", resulting in a far slower print.
2) The interface where the top of the support structure and the underside of the model meets was quite strong, making removal of the support more difficult than necessary.
a) The ability to specify the size, material and density of an interface layer which goes between the model and the support would be very useful, particularly for conserving PVA when printing support material on a dual extruder.
b) This same ability could be used to make a weak interface layer, by setting the interface layer height to one layer, and its density to zero.
3) An option for "underside only" support, which would only create support between the printbed and the model would be quite useful (at least for the model I was printing).
