We bought it for the 9yo for his birthday. He loves it, and I think it's a keeper.
It could definitely get expensive with add-ons, but the starter kit is actually a great deal. You technically get 3 complete games, which they call 'playsets' (Pirates, Monster's Inc, Incredibles) plus the Toy Box where you can play and build anything you want. You will have to buy an additional character for each playset to make it 2 players though. He's excited for the Phineas and Ferb characters to be released.