We've had a 5904 since back when the 3rd generation guns were the latest design from Smith & Wesson, it's a great gun.
Good accuracy, points well, looks great, very reliable. Would never sell it.
Once I wanted to see how dirty it could get without a malfunction. I just kept shooting it on various trips to the range, no cleaning, no oiling at all. Got to about 750 rounds before the slide wouldn't close fully after firing the previous round in the magazine (may have been an ammo issue, possibly the previous round was a little light on powder and didn't have enough oomph to work the slide fully). Just racked the slide manually to clear that round, the next round loaded in easy, and it kept right on firing after that for the rest of the range session (probably about another 150-200 rounds) without any problems. That's rather impressive.
It was really dirty when I cleaned it after getting back from the range.
That's the kind of handgun I want, one you can put a few hundred rounds through, get it dirty, then stick in a holster with no cleaning and be sure it will fire a few more mags if you need it for real. Guns that have to be really clean, like some tack driver match guns, or they don't work reliably, are no good for serious use. You can't afford weapons that are finicky like that when you need them for real.
I think S&W should go back into at least a higher limited production of these guns. Make them a normal catalog offering. Quite a few gun owners would buy them. 10mm fans would especially buy the big steel 10mm guns right up, beautiful and built like a tank, they are perfect for shooting full power 10mm ammo.