Having played the game quite thoroughly, I have to agree it's not worth the price. It should be priced $10-$15.
Sure there is a lot of replayability, but the experience is not largely different or varied to justify it's current price.
Remember, that the next-gen versions were $40 originally. They smartened up and reduced it to be $30 with the older versions. When a new game is at $60 MSRP, being half the price of a full retail game should give you half the experience of a full retail game.
This game does not meet that requirement. Being priced more than some XBLA or PSN Store games is not a trend I want to see continue.