Wasn't It Kinda Obvious After American Idol? E!Online reports in "'So You Think' It's a Copycat?" From the article:

Some of the supposed similarities between the Fox show and the plaintiffs' original idea listed in the lawsuit include:

It's a 60-minute show.
It recruits contestants from around the country.
A panel of professional judges--including a snarky British guy--evaluate the contestants. (That's not exactly how the complaint read, actually?)
Non-competition scenes, such as practice sessions, are woven in with the performance sequences.
The competition involves pairs dancing, as well.

Actually, it's starting to sound a lot like Dancing with the Stars.