I own the 360 and the Wii. I take very good care of them, but i've had the misfortune of having numerous hardware issues with the 360. Not everyone has hardware issues with the 360, but if you do Microsoft replaces the unit you ship to them with a refurbished unit that may not be up to spec with what you sent in. This can cause more issues since you never know what the person before you did to the box (towel trick, etc...). If you're really considering buying the 360 I'd recommend that you go to the xbox.com message boards and read up on the hardware problems. Living in upstate NY it takes about a month for the whole repair process for me.
The 360 does have great games, but the online costs money to play against other people, plus if you want wireless its $100 for the adapter. I'm a bit biased due to the ammount of time and money i've wasted on the 360 so i'd recommend getting the PS3 if you're looking to get another system. If you're one of the lucky ones to get a 360 that doesn't have any hardware issues its great, but once you go down the hardware maintenance route it never ends.