Go read this Baseball Prospectus article now - it's free, and it's about the Astros. They've done some neat things with analyzing not only which baseball parks are good for hitters and which parks are good for pitchers but separating that out into if parks that are good for hitters are especially good for right-handed hitters or lefties and the same for pitchers. They've found (as you would expect) that The Juice Box is incredibly good for righty hitters (check out Ensberg and Biggio's home / away splits sometime) but average for lefty hitters.
This makes the Preston Wilson signing even better, and it makes Jeff Weaver an interesting option - he dominates righties, but struggles against lefties. Read the article for more.