I'm a big dance game fan. I've played all of the DDR mixes, US and Japanese, extensively, and a hell of a lot of ITG as well. At this price, it's a steal. Is it better than DDR? No, unless you're the type of person who can only enjoy themselves on 10-foot songs or higher. If you don't know what that means, then you're definitely going to have a better time with DDR. The steps are (IMO) much more fun in DDR, even if they don't go well beyond humanly possible in terms of difficulty. And let's not even get into the load times.
That being said, I've had a blast with ITG. Over 70 songs, some of them a lot of fun (Utopia, Land of the Rising Sun...), and a fun new twist on Nonstop mode. Don't expect it to be better than what else is out there, but you'll get your $20 worth, no problem.