Martin had a pretty terrible second half last year and is doing poorly to start this year. I think the 19 HRs he hit in 07 might end up being his ceiling as far as HRs go. He slugged .468 that year, while his career average is .423. He is taking some pretty big swings this year, but he's good enough to make an adjustment (his K rate will likely come down). The Dodgers as a whole haven't been stealing much, but with the loss of Manny and addition of Pierre to the lineup, you should expect the speedy Dodgers to start running more.
Martin has been a bit abused so far in his career and generally catchers who play as much as he has tend to wear down. I'm willing to be that has something to do with the slow start though I'm sure some of it is just a slump in general. Taking a catcher early is never a good idea though, you have to treat them like pitchers and devalue them since their injury/burn out rate is so high. Best bet is to aim at those 2nd tier C that can sometimes jump up to 1st tier production.