Where the Wii was being demonstrated (don't worry, I'm not posting any spoilers for TP).
Unfortunately I didn't get a go (too many people crowding round, and I didn't have that much time), but I must say I was very impressed by how well the system worked in live tests. The games on show were Wii Sports, what appears to be a version of Wario Ware, another bunch of mini-games including air hockey, and of course Twilight Princess. I got a good luck at one of the setups, and the sensor bar was stuck on to the bottom of the screen (a nice widescreen TFT) with blu-tack of all things! The bar itself is about 1/2" by 1/2" by 8", give or take a bit. The Wiimote also looks surprisingly small and 'chunky', compared to a usual TV remote.
Looking at people using it, it looks like the controller takes a bit of getting to grips with. Then again, it's not that dissimilar to learning how to use a computer mouse. Wario Ware (or whatever it was) seemed to be the most innovative, by getting you to do such things as swat flies, crank the handle on a paper shredder, write on a piece of paper, and steer a car around. The air hockey was fun to watch - it looked like you were pointing the Wiimote where you wanted the 'sticks' to go, which made it tricky to line it up for throwing the puck around. Having played a PC version (there's a nice one in the DirectX SDK), I can see how hard it could be to begin with. An earlier group seemed to have no trouble after a minute or two, so lets hope I can pick it up easily.
Moving on (skipping Wii Sports as I didn't get a good look at it), we come to Twilight Princess. I'm going to try not to post anything that hasn't been broadcast all over the interwebs (or that you won't find out about 5 seconds in), but if you want the entire game to be a suprise then do not click the cut.
Still here? Okay, what they had was the fishing mini-game and a small dungeon run-through (the one that was showed at E3). No-one played the fishing game while I was there. In the dungeon you get a bit of moving around, some playing with the boomerang, good old hacking and slashing, and the bow and arrows. Aiming the bow looks very hard, but at the same time very intuitive. You don't appear to be able to 'hold' it in a position as well as you could in the earlier games, but you can quickly move it around. They guy playing was pretty poor to begin with, but picked it up reasonably quickly after a few false button-presses. The boomerang can do Wind Waker-style multiple lock-on, but unlike Wind Waker it looks like you have to press a button to lock on to each target. Spin attacks look stupidly easy to do with the Wiimote-nunchuck combination, no more faffing around with the timing getting it just right. The game engine is blatantly a modified Wind Waker - things like the enemy explosion sounds and some of Link's animations are taken straight from it. Link also does the Wind Waker trick of looking at interesting things. Speaking of engines, it looks rather polished: things like particle animation work, dynamic lighting is looked good, and it gave the appearance of mostly doing what you expect it to do. A Navi-like fairy is the 'pointer' for the Wiimote, but fear not - a character with annoying hints is there! Active controls appear vertically on the right - D-pad does item selection and looks like it might be able to scroll through items, possibly a little like StarFox Adventures did. The guy playing seemed to end up pressing the wrong button a few times, so watch out for this.
Okay, that's the end of the OMGWTFTPLOLBBQ section. They also had a few DS's there, with StarFox or similar on them. Plus there was also a competition to win a Wii, to which I thought "worth a try" and filled one in.
Edit in Feb 2017: finally uploaded the photos. Only took me 10 years to do!