I just picked up a slightly used S&W 642 at a gun show Saturday and I'm very impressed with it's lightness and how it shoots.
Yesterday, I took it apart and did a trigger/action job, cutting a couple of coils off the trigger return spring and lightly smoothing most moving parts, using India and Arkansas stones, then buffing compound on a Dremel wheel. I was surprised to see blued steel internal parts, which will wear better than most stainless, as long as the hardening isn't cut through. I like it better than stainless parts coated with hard chrome or other metal. Most of the parts were pretty smooth as it came, but there was a burr on the forward portion of the trigger where it engages the locking bolt.
The trigger pull increases in weight for about 2/3rds of the travel, then levels off and has a very smooth let-off. It's one of the nicest double-action pulls I've found in small handguns.