I've now see all of Season 1 and part of Season 2. For TV it's quite good--a solid three, maybe light 4, though Season 1 was better by quite a margin. It took me a bit to get used to John Krasinski in the Ryan role, but now I think it was great casting--he's able to convey the brilliant-reluctant-hero personality that was so important to Clancy's work.
I should note that neither of the seasons do justice to the overwhelming technical details of Mr. Clancy's early writings. (The later ghost-written tomes were simply embarrassing dribble). I hope that things get better as I finish Season 2, and that a potential Season 3 can at least get us back to where Season 1 was so entertaining.