Got to see this thing up close at the mall I work at. If your local mall has a Microsoft kiosk or you have a Microsoft store, see if they have it. I got to hold the controller too.
The controller's 'wings' stick out more and that was the first thing I felt. The sticks were smaller and covers more your thumb tips than your thumb print if that makes any sense. The shoulder buttons are basically that whole shoulder. The triggers were tight but after days of gameplay they may loosen up. The buttons feel good, I guess.
The dpad clicks for a responsive feel though I would have like it a tad bigger, and they 'dip' downward rather than completely face you which felt weird. I 'shadow-boxed' some Street Fighter routines on both the left stick and dpad and I think the controller will feel natural pretty quickly. The back not having having a battery lump is bigger selling point than they're saying - very cool.
And I can say it still have a meaty weight to it that nobody seems to be talking about. I like a good gravitation resistance rather than something that feels flimsy (like PS3's controller). Happy to say the weight, while lighter than 360's controller, met my standards.
Lastly, the console is MUCH slimmer than what pics made it look. More inline with 360's size without the pretentious curves that mean nothing. Hardly the bulky 'cablebox' I thought it would be. They had no games to demo, though.
The guy at the desk had no issue/was probably bored enough to take it out the case and let me molest everything, and I'm at the mall often so if anybody wants specific shots or more info I can see what I can do.