yes Brant, the lack of a dropped toptube. I dont like running extremely long seatpost extensions, I'd rather have the seattube there to support it but also have enough crotch clearance for slow almost trials stuff and also for a bit of asthetics, allthough there are probably sound design reasons why you didnt allready do it.
However im comparing the Bluepig to my existing Chameleon and the BFE with their 'dropped' toptubes, and the Transition and Evil both with their DialledBikes-Alpine style dropped and braced toptubes.
Like I say the 16 and 18's 'look right' because they're small and squat, and look like a bike I could batter the absolute crap out of……apart from the fact they're too small. The 20" dosnt though-it looks a bit old school XC-ish if that makes sense?