Patrick from CrumplePop (btw go check their products) just sent me info about his workflow to achieve ridiculous slow motion effect without using Twixtor. The process is quite simple: shooting at 60fps and retiming in Motion using optical flow then play back the clip at 24fps.
and the result:
I have to admit the results are pretty good. I tested OF a while a go (at a much more reasonable fps) and did not like the results. Probably I was using sub optimal footage.
Has Patrick said in his blog post, using a tripod and a simple (and static) background is key here.