I beat the game last week. It is fun, but it does have it's share of problems. Some times, in the middle of combat the AI gets confused and you have to stop, and re-set a fight so you can figure out what's going on. I also don't like how you can't move when you've deflecting with the shield. The combat can be a lot of fun, especially when you string attacks together. I would say that the biggest draw back is the ridiculously repetitive settings, the simplicity of the boss battles, and the overall run time of the game. I've purchased all of the movie tie in games this Summer (Thor, GL, Transformers, Cap) and this ranks among the best.
Is it worth $50? Sure, if you've got the extra money to spend and you're a fan. Otherwise, wait for a price drop, or give it a rent.