It feels unfair being overly critical of an Xbox Live Indie game. For a measly 80 Microsoft Points you know you're not going to get an experience on-par with the best games out there, but we must still be truthful in our critique of Avatar Superstar.
The screenshots and branding suggest that this is a karaoke experience, whereas the reality is slightly different. Although your Avatar does take to the stage and you're encouraged to sing along, there are no lyrics and no scoring: you're just doing this for fun. You can choose a song from your Xbox 360 music library or sing along to one of the built-in backing tracks, turning the game from karaoke to musical improvisation. If you're the sort of person who loves making up songs off the top of your head, you might warm to the concept; others might be put off by the lack of 'proper' songs.
While there's no scoring, a gauge at the bottom shows your tone — "good" or "bad" — and levels show how loudly you're singing. Kinect does a decent job of picking up your voice — after all, it's got nothing else to do here — although in playback there's some inevitable echo and crackling. You won't be putting these tracks onto CD though, so it's not really a problem.
When you've warbled your way through the song to the best of your ability, or simply had enough, you can replay your performance, turning auto-tune and echo effects on or off, then sit back and watch your virtual-self strut up and down the stage singing the song you just made up. If that's your idea of 80 Microsoft Points well spent, this is the game for you.
You can't really gripe about 80 Microsoft Points, even if it only buys you the chance to see your Avatar parade around a virtual stage singing along to your recorded performance. If you have a spare 80 MSP in your account, you might want to consider it; otherwise, don't buy a points card just for this.