I've recently been using Purple Power industrial strength cleaner/degreaser, at the recommendation of the guys at an auto-parts store where I sometimes buy touch-up paint or other things for working on bikes.
It works fine, feels very detergent-y (in a slimy sort of way), hopefully isn't corrosive like Simple Green, but doesn't function as a true solvent and leaves a lot of suds and residue. And it also doesn't lend itself to re-use as mineral spirits does.

Next time I think I'll go back to mineral spirits.