A Great Idea...
I always love the idea of a multiplayer flash game with a chatroom function and so I did try and play this for a while... but I couldn't.
The gameplay (maybe it is just my computer) was fairly choppy and slow and I don't think the chat worked. I'd suggest working on the graphics a bit more too - I was supposedly playing a co-op battle but I didn't even know who were my teammates as some of the characters didn't even look like anything in particular.
Other than that, it seemed like a great idea - the menu worked well and was simple to navigate and the controls for the game were simple enough... the game does have quite a lot that needs working on, though.
It's such a great idea, but I do think you should keep working at it to improve the game and make it more enjoyable for the players. I hope I have helped with writing this review: 5/10.