I agree he was a bit stiff in the first season, and anytime he had to act really excited it came off a bit forced, but that didn't happen all that often. For the most part I thought he was fantastic, and nailed just about every line he delivered.
Although I do wish they had played up his sarcastic humor a bit more. His exchanges with Bashir in "Cardassians" crack me up every time: "Don't apologize, it's been the high
point of my day" and "By all means. Will one
Runabout be enough?"