Without giving away major spoilers, I can say the following:
I love Greek and Roman mythology. I went through a phase in my youth where I devoured books about it. This movie raped my childhood. I am, perhaps, a bit harsh, but I'm also coming from a childhood where I grew up watching the original 1981 Clash of the Titans movie. This aint it.
In my opinion, the film makers decided they wanted to make the bad-ass mother of all monsters, the Kraken, and then just kind of fudged a story around that. I was never able to emotionally connect with the hero Perseus (played by the main guy from Avatar). He seemed surly and angry and brooding the entire time and *checks IMDB*
In order to drive the plot the filmmakers throw in a bunch of random sketchily described characters that thankfully you never really get attached to since you know they're all monster-fodder for the most part. The hunters are amusing, if albeit a complete mystery as to who they are or why they are even in the city.
The liberties taken with traditional mythology had me grinding my teeth throughout, and a few times I was like WTF seriously? UGH.
The action scenes were for the most part so rapid-paced I feel like I missed half of what was happening. The whole movie felt rushed, thank goodness for the plot device of having someone with them the whole time that "knows the way". What a time saver!
Now.. having said all that, I can tell you it was at least entertaining, esp I'm assuming if you have NO knowledge of the prior movie (psst.. watch for a nod to that movie in this one -- that was awesome!), and NO knowledge of mythology. The kids liked it far more than I did, being less critical.
And, Pegasus rocked. No, seriously. Like.. they did such a good job on him I was in awe. I want him. Did I mention my favorite-ist horse breed in the entire world is Friesians? Now, take one, add REALLY good cgi wings. Yeah.. instant WIN. I admit it, I'm a horse lover so I notice horses in movies. Friesians tend to be used quite a bit since they are so striking, elegant, and have amazing natural action. Lem has told me he'll go back to college for genetic engineering and will find a way to splice wings onto a friesian. He's da man.