I do wish his strikeout rate would go up and walk rate would go down. I've heard a lot of people say that he's not throwing his out pitches in two-strike counts, which would help towards that; I haven't watched Buchholz enough to confirm/deny that, but if that were true his peripherals (which are not good) could, at some point, support his ERA.
In his first 100 or so innings with the Sox, Buchholz had a K/9 rate of about 8.5, 8.6. The next 200 innings, his rate is about 6.5 or so. He's been adding velocity through the years, but now throws his slider more and more while really dropping down his curveballs (8% this year, 15% and 21% in 07 and 08) and his changeups as well, although to a lesser degree.