In the pages of this site the 915 has a large, vibrant following. If you are brand new to the 915, here are some points that aren't obvious.
1) S&W messed with a lot of people's heads with their choice of 9-1-5 for model number. Before this pistol, all the 2-digit metal frame pistols were "1st Gens", the three-digit models were "2nd Gens" and the four-digit models were all "3rd Gens." S&W named this one the 915 but make no mistake, it is absolutely a 3rd Gen pistol. The odd name was a simple "9mm/15 round magazine."
2) This pistol was a S&W error! Wait, don't get mad, I am not slagging the 915. What I mean is that S&W intended to make a cheaper version of their flagship duty hi-cap 9 and the 915 was that attempt but they failed at their goal. They didn't cheapen it down enough and that's why it only lasted a couple years. Even so, this pistol is NOT SCARCE and don't buy any "they are getting hard to find!" lines because that continues to be nonsense. I dare anyone to search Gunbroker for the availability of 915's. S&W made a zillion of these over only a couple of years.
3) Short version is that a 915 is a lower-cost, lower priced version of a 5904. The frame is slimmer, the finish is cheaper, the sights are much cheaper and the decocker is single sided. Otherwise, this pistol is a fully capable alloy frame substitute for the legendary Model 5906. Any parts for a 5906/5903/5904 with the exception of sights work with a 915.
4) Yep, S&W goofed on the 915, made it too good and not cheap enough. They ended it when the Crime Bill/AWB became reality. It was replaced by the Model 910 which is much cheaper in many ways. I am no fan of the 910 whatsoever but I won't slag it since some owners might get miffed. But the 915 is way, WAY better than any 910 could ever hope to be.
5) the true genius of the 915 is in use. Yes, you can think, hope and dream that one day it will be "collectible" but I think that is a pipe dream. They made a zillion and they go for low money. Buy one, run it hard and love it. It's not gonna be a collectible in the next 25 years.