I've been able to put in about 4 hours with the Wii since it arrived Monday morning. The quick verdict is the Wii lives up to lofty expectations. There are definietly some minor issues with the controller sensitivity at times, but it's nothing that really distracts from the overall enjoyment. The initial system update also took far too long (Upwards of 30 minutes) but i'll attribute that to Nintendo Server overload. I was completely unable to find the Nunchuck controller for my additional Wii-motes, so all my multiplayer experiences were with Wii-Mote only. Now i'll give a very quick rundown of the games I was able to play yesterday. I will post full reviews once I get to put some more time into the games.
Wii Sports

This was the first game I threw in, and it's not that great as a single player experience. Tennis is ok, but not controlling your character will cause some confusion as to which way to swing the controller (Forehand or backhand). Baseball is what everyone expects, simple batting, simple pitching and no fielding or baserunning. Bowling is by far the best on the disk, especially in practice mode where you'll eventually try to bowl down 100 pins at a time. Golf is suprisingly realistic in the control scheme and will probably not work well for non-golfers. Boxing is alright, but it turns into a "who can shake the controllers faster" experience.
Wii Sports as a Multi Player experience is a completely different, and much better, experience. Tennis instantly becomes tons of fun when playing doubles side by side. Baseball is also boosted when one player is pitching to the other. Bowling gets better the more people you have at the lanes. Golf is still golf, single player or no. I wasn't able to try Boxing due to lack of extra nunchuck.
Madden 07

I've only put in about 20 minutes with Madden as I only went through practice mode and a couple mini games. I can say with confidence that this is the best Madden to date and should prove entertaining to a much wider audience than any other football game to date. The controls are simple and will come naturally to almost everyone. Passing is a bit easier, but the real improvements come in the Running game. Jukes are done with a quick shake of the nunchuck, stiff arms with a flick of the Wii-mote. Lack of a second nunchuck prevented me from playing this multiplayer.
Super Monkey Ball: Banana Blitz

I have not played the single player game yet. I have tried about 10 of the 50 or so mini-games. I am dissapointed to say that i'm unimpressed thus far. Out of the games I've played, only about 2 made me want to play them again. The control on some of the mini games is not explained well enough and seems broken at first. After a couple plays, the control schemes come, but more than half of the games I played didn't deserve a second shot. I have to put more time into this as Monkey Ball was my favorite multi-player experience on the Gamecube. For now though, i'm a bit disappointed.
Rayman Raving Rabbids

This is an absolute MUST BUY game for anyone with a Nintendo Wii. You will not laugh harder at a video game. Ever. I've only played through about 10 of the 70+ mini games, and 9 of them were Amazing! (The 10th was just a bit too hard for me. How do you throw a cow 60 feet?) If you own a Nintendo Wii, please do yourself a favor and at least rent Rayman. I doubt i'll have more fun with a mult-player game this year.
That's all i've got for now.
Mahalo