The singing formula is solid. The dancing is fun. It just feels it's missing a few things...
What's also needed for music games is a Practice mode, and this game doesn't have that either. So it's trial-and-error, in the most extreme situation. Be prepared to play songs over and over until you've got the pitches and moves correct. So if you don't know all the songs perfectly, be prepared to struggle until you get them.
The game has a great setlist to choose from, but it seems to be lacking here as well. Only 30 songs to choose from. That's much less of most rhythm and music games that I've played. The rest you have to buy, and I'm not the biggest fan of shelling out cash for additional content, especially if the game had so little to begin with.
The singing and dancing are fun. The dancing can be hard to imitate, but with practice it's doable. The accuracy of the game to detect correct notes, rhythms, and movements is also not that cohesive. A few times, I was singing a wrong pitch that ended up with a "cool" or "good" rating, and vice versa.
Overall, Singstar is a fun, simple party game. But perhaps too simple. It would really benefit the franchise with added modes and more options and accuracy could be better. It just doesn't seem to live up to the competition the genre faces.