Thought it was pretty damn good. The action on the sub was really intense, and the idea of these guys being targeted by both the government and their own Navy is a really cool and compelling one (maybe one of the best since Lost).
Unfortunately the prospect of spending most of the series on this island isn't grabbing me as much. I'd rather see the crew constantly on the run (ala BSG), since that's when the episode was at it's most exciting. Plus it just feels like a more unique setting than yet another tropical island.
And all the constant cutting back to DC was a distraction too. I'd much rather keep whatever's going on there a mystery, and have the audience be as much in the dark as the crew is.