It's just a great guitar. I've always felt that anniversary models can be of the same extremely high quality as the J-customs, but ~800 is still a lot of guitars for an expensive, limited edition, anniversary model. I've seen 3 Jem90HAMs, and they were on par with the JC's. Great fretwork, smooth neck, excellent playability, in-your-face-tone, brilliant looks. They even thought about matching the headstock to the body.
Playing a Jem90HAM (Any HAM I should add, though I've never played a JS90, but if the JPM90 and PGM90 are a any indication) is an absolute joy. You have to get used to the absence of inlays, keep the sidemarkers as reference points.
Despite not having a vine, pyramids or some other inlay, they are Jems first. It's not a BSB or a VWH or a 10. But in the end it is still the shape we know, handle and claw, evo's, lo pro. IMHO the metal pickguard helps the tone as well as the looks, but they are tough to keep clean. Wear, sweat and body acids will stain the pickguard. The paint can also wear. This has to do with the "stucco" sublayer. The finish can also wear your clothes, so watch what your wearing.
Perhaps I've forgotten something, you may also want to check out the search, I know there is a thread on Jem90HAM vs J-Custom RG-metal.