On the subject of hats, one of the first things I thought about while watching this movie was how disappointed I am in Valve for not capitalizing on this movie's hat potential. The hats in Immortals are seriously amazing. I would wear King Hyperion's Pinsir every single day. For reals.
Of course, there are definitely a lot of drawbacks. I would say I only knew what was going on maybe 75% of the time. I understood what people were saying far less than that. There are a lot of accents, a lot of dialogue that is rushed, and a bit of mumbling. I don't know anything about Greek mythology so I can't speak to the accuracy on any of that, though I have a feeling they didn't particularly care about getting anything correct.
In the end, I would definitely recommend it if you are interested in the cool visuals and can give a pass on the rest. Plus Mickey Rourke is always all kinds of badass.