Dave Cameron at Fangraphs has a nice article analyzing Hampton's performance so far this season. Cameron decided to examine Hampton because he ranks (unexpectedly) in the top 10 of strike out pitchers so far this season, right behind Lincecum. He provides some pitch F/X graphs if you are interested in that type of thing. His conclusion: Hampton has several pitches, not much velocity, but lots of movement. As stated in the article:
Hampton throws five distinct pitches - a four seam fastball, a two seam fastball/cut fastball, a curve, a slider, and a change-up. He mixes them extremely well, alternating speeds and keeping hitters off balance. His two seam fastball and change-up have similar movements, adding to the deception. His curve and slider are distinctly different, and he’ll use the slider more against right-handed batters. The change-up is almost exclusively used against right-handed bats, and is the main reason that he’s actually been better against RH batters than LH batters throughout his career.
There’s not much velocity in there, but in terms of being able to vary his arsenal and keep hitters guessing, Hampton has a really good repertoire of pitches. He’s not going to keep striking hitters out at this rate, but for as long as he can avoid the Disabled List, he’s going to be a solid starting pitcher for the Astros.