Okay.
Xbox live= the most amazing thing I have ever used. And I have the free Silver account. Dowloading videos and games and so much more. It's amazing what the online service has for the 360.
Game-wise, the prices of games are dropping in price now. Games that used to be $60 are dropping to $50 and $40, some even more. There are many good games, such as Gears of War, Viva Pinata, Guitar Hero 2, ect, ect, that are worth the money. (And Halo 3 is released this fall) Also, more Xbox games play on a 360 than people say. There's a list where you can see if the game is compatible with the 360, so long as you get the more expensive ones. The Premium and Elite versions save money in the long run.
I wasn't too keen on a 360 for a long time, but I recently bought one so I would have one in time for Halo 3, and they completely surpassed my expectations. The Wii is cool, but the Xbox 360 will blow you away. It is worth all the money you spend on it. It's nothing short of amazing, and, frankly, it's far beyond amazing. The online service was really what blew me away the first time I played my 360.
If you're considering it, get it. You will not be let down.