I loved it, my main reason for watching the original Iron Man was Robert Downey Jr so this one was great in that respect. The start with the voice-over/narration style instantly reminded me of the same thing in Kiss Kiss Bang Bang which i thought was a nice little (maybe) reference.
I felt they could have gone even further with Tony's vulnerability but it was a nice change of pace from his usual cocky attitude.
Since i've never read the comics
I'll be going back to see it a couple more times while it's on, the Unlimited Card will pay for itself well this month!