I've stayed at the Treasure Island a couple times and I absolutely loved it. It's a cute little hotel, has a nice and hip and happening pool, and the Sirens of TI show is really fun to watch. As a kid I would watch the old pirate show, which I remember as a lot more kid friendly. It's obviously not the nicest hotel you can stay at in Vegas but if you want a good deal for an awesome location (on the strip and near the many other hotels), then Treasure Island is a good bet.
Oh, and their buffet is AWESOME.