All the stores have a single prototype on display for people to play with. I tried it out today, and it was the same as on the web. Perhaps the most striking thing was how inadequate it made the other MP3 players look. The display and interface is miles ahead of anything else. It's immediately usable. I couldn't fathom using a Nomad Jukebox after playing with it.
Everything about it is cool. It sounded pretty good, but I think the lack of an EQ quickly becomes a sore spot. Most songs sounded good, but when I tried some bass-heavy tunes (they didn't have many on it) I had to turn it up pretty loud to get it to thump. I tried an Oakenfold tune, a DJ Dan tune, and a Ramstein tune (that another board user put on). I don't think it was the headphones. I think the device itself is way too flat.
Overall, it is a breakthrough product in that market. I was very impressed, and can't wait to get one of my own. This is the MP3 player that makes them worthwhile. I'm convinced that any device without firewire is a waste of time (quite literally!)
-Paul