I bought this game (which is on the XBOX 360) when I traded in my Wii. I was amazed about the not one but two wireless mics that come with the game (that aren't compatible with any other game and have been reported to sometimes lose signal btw). Thats really the only downfall about the game because it's really got some awesome features like real music videos and complete lyrics, and the option to play different battle and mini game style karaoke face offs. Plus if you have more than one friend over they can grab a standard controller and play percussion while waiting their turn.
If you happen to have a zune (or a portable usb hard drive) they are totally compatible and you can sing along to the music you have on either of those devices sans the videos and lyrics. Granted for those songs that there isn't a real video you are given a couple generic vids to pic from so that it at least gives you something to watch while singin' your heart out to some Tina Turner (yeah big fan!)
The game starts you out with 40 songs and you can always download more from the xbox marketplace. I've downloaded something like 8 songs from the marketplace and can't wait to see what else they add at a later time. I would totally suggest this game for those of you who have a 360 and for those of you that don't GO GET ONE! No really it's an awesome system.