It does look nice - it looks like HL2 on my GF7800GTX with all the effects turned up to full and antialiasing up high too. The glimpses of Kong I saw at the HMV demokit looked the same - high quality. I don't know if those were HD kits or not, but I do know that the PS2 they had running a little down from it looked horrible in comparision.
From a usability and functionality point of view there's not much that could be gathered about the console itself; the controller is the same one I've had on my desk for the past couple of months, and most of the 'Xbox Guide' system software was locked down on the demokit. Bringing up the guide mid-game seems very smooth though.
Kameo looks enjoyable enough, though don't let the elements aspect fool you - it's "the player can do 12 things," just grouped into four groups of three, and you select a group to work with at a time. It might just have been the screen there, but it seemed very dark - the demo level is 'Thorne's Tower' and I played a section which involves rolling up ramps on the walls to get to higher ledges or to get over walls. In a few places, if you're not looking closely, the ramps are not very visible.
I'll probably go down again sometime soon and check them out some more, see if I can mess with any other games.