They're real workhorses ...
If your pistol has a "stainless appearing" carbon steel, flash chromed hammer & trigger, square trigger guard, and a narrow barrel tab, then it's an early 3rd generation pistol ... and you should check your grip to make sure it's the current one, and not involved in the early recall.
To do this, simply take your EMPTY pistol and turn it upside down so you can see the bottom of the grip. Locate the "U" shaped notch in the grip material ... look to the immediate rear and front of the notch ... you should see a small "dimpled" spot, which almost looks like someone poked it with a heated ball point pen. If you can see a small indentation, or dimple, in the grip material at either of these locations, then you have the upgraded grip. No problem. If you don't, call S&W Customer Service at 800 331-0852, ext 2904, and tell them you need the upgraded grip. 59XX grips are available in either the original arched shape, or a flat backed grip ...
If your pistol has the early narrow dovetail rear sight, you can still find some optional sights. If it has the slide cut & milled for the longer (front to rear) Novak Lo Mount dovetail sight, then there are a LOT of optional sights you can have installed ... if you don't like the standard sights.
I've carried a couple of 5903's, and then 6906's, for a number of years since we adopted them about 1989. I still carry the 6906 often for plainclothes, although I also carry a SW99 .40 S&W.
I've fired thousands & thousands & thousands of rounds through these 9mm pistols. I've watched somewhere between 750K-1M rounds fired downrange through ours. Last time I checked, I was somewhere between 12K-15K for my current 6906. I replaced a sear release lever (LOTS of decocking) and recently noticed my original extractor was starting to chip. This isn't uncommon on high mileage pistols, as the extractors can become "work hardened" over time, and therefore brittle. I replaced the extractor because I could, not because the pistol had malfunctioned, though, as it was still extracting & ejecting totally reliably. I just noticed it during a detail strip and decided to head off any future malfunctions. I also replaced almost all of the springs around the 12K mark, just because ...
Check out the Smith & Wesson Forum for some other info, and really great folks ...
http://www.smith-wessonforum.com/cgi-bin/sandwcgi/Ultimate.cgi?action=intro&BypassCookie=true