I don't have one, but considered picking up a Little Phatty numerous times. I see them on Craigslist for about the same price as the Slim Phatty, although they are always the first model (which can be upgraded). One that I passed on ended up in my local GC, and I got to try it out there. It sounded great, although not quite as thick as a Voyager, but it's not $3500.
It's an analog synth with the classic Moog sound and filters, so it's suited for whatever you want to program into it. I have an extensive amount of softsynths and in my opinion very few come close to a true analog sound. XILS lab, DCAM and to a slightly lesser degree the Arturia stuff are the only VST's to my ears that even sound close to real analog. I love my Massive, Electra X etc. , but to me good digital is good digital. By that I mean I probably wouldn't ever buy a Virus because I feel I can achieve a similar sound in the box, but I would definitely buy a real analog synth, because I hear the difference between the virtual and the real thing.
The Phatty's are monophonic, so think about how important polyphony is to your workflow. Personally I think I'm going to go with a Dave Smith Tetra over a Phatty, because even with only 4 voices, it's a lot more versatile. I'll miss out on the general character of the Moog and the creamy LP filter, but the Dave Smith stuff sounds good too, just different.
