Better off singing along to the music videos on MTV.
The way the pitches come up on the screen is confusing, and there isn't much difference between easy/hard mode except that the notes are longer. In fact, the scoring system is so impossible that even while singing a song you are very familiar with on easy mode, it is virtually impossible to attain a perfect score. The game doesn't give much room for artistic expression, and only allows harmony in *some* parts of *some* songs.
I found the echoing of the mic so annoying that I had to turn the volume right down, and it picks up a lot of rustling and interference. The 'rewards' you get for completing the challenges are simply badges that do nothing. I was hoping for some unlockable songs or modes. And the choice of songs could've been better; when I saw Taylor Swift on the cover, I thought there might be some Love Story or You Belong With Me. Instead there were a couple songs I previously hadn't heard, and that I didn't particularly like.
Probably my biggest issue with this game is that there are no volume controls other than the mic; you can't change the volume of the original lead vocals. This means that you're just singing along to the studio version, over the original vocals. Not very Karaoke-like. It's like they slapped some subtitles onto a few music videos, and passed it off as a video game.
Lastly, a lot of the game is available only if you have two mics, which is inconvenient. I'm not going to buy a second mic just to play a game that isn't worth the money.
All in all, you might get a couple hours of fun out of this game, maybe more if you've got a couple mics and a few friends, but wait till you can find it on sale. Can't say it's worth the $40.