Was just about to start a thread on Stewart, even though I think there's an old one floating around somewhere.
I really hope he continues to see regular playing time. He's by far Colorado's best source of power this season, and I think you're right that with regular playing time his average would improve - it would likely settle in the .270 range. I think this kid has legit 35-40 HR power, and its unacceptable as a manager not to get that kind of bat in your lineup on a daily basis.
Speaking of Colorado, Atkins batting cleanup is absurd. Helton batting 3rd is fine. Hawpe should be batting cleanup, followed by Stewart, and then Atkins in the six hole. It's a completely useless experiment that I hope ends very soon. The only potential reasoning for the move is that they're hoping to jumpstart him, get him some good RBI opps to showcase him for potential trade partners.