Let's be clear: I don't want to like Glocks. I've spent ~25 years not wanting to like them. They're plastic, ugly and soulless. They're also light, reliable, and decently priced. Harumph.
With that said, I've had very limited experience with the G19, and all I can say is that I don't want to like Glocks, but that's the model that might force me to begrudgingly change my mind. A few years ago, a buddy loaned me his to carry while one of my pistols was in the shop. I carried it for a few weeks, but never shot it. Then, a couple of weeks ago, I got to put ~150 rounds through a Gen4 G19. I'm much more a "1911 guy" than I am a "Glock guy," obviously, but here are my opinions, worth exactly what you've paid:
1) Reliability -- Certainly, the Glocks have a stellar reputation for reliability. My experience was limited to ~150 rounds of 115 grain FMJ and a little bit (10 rds) of 147 grain BJHP. The only malfunction was clearly ammo-related. (One of the 115 grain FMJs actually separated from the case during feeding.) Other than that, the G19 ran like clockwork.
2) Simplicity -- When I got the G19 in hand, I field stripped, cleaned and lubed it. Now, y'all don't know me, but as a general proposition I'm what you might call "mechanically reclined." I'm not a tinkerer. With that said, getting the G19 down for cleaning might as well have been covered in "Field Stripping for Dummies." I've never found it difficult to strip or clean a 1911, but the G19 was so, so easy. Reassembly was easier than a 1911, IMO.
3) Accuracy -- Are there more accurate guns out there? Yeah, probably. Is a G19 accurate enough for HD/SD? Absolutely. My first group at the range with the G19 wasn't great, but the RSO was kind enough to give me a few pointers, and my groups shrank to acceptable proportions in very short order. Frankly, I'm convinced that the G19 is probably more accurate than I am capable of shooting.
4) Weight vs. capacity -- I carried that G19 that belonged to my buddy for a few weeks, and it was comfortable. Mind you, I'm not uncomfortable carrying full-sized in steel, but I have to believe that the G19 is even more comfortable. I could carry that all day without a second thought.
5) Caliber -- *sigh* I really and truly like the .45 acp. It's my most favorite of the SD handgun rounds, plain and simple. However, I consider 9mm to be "within the window of acceptable performance." I wouldn't feel undergunned if I had to carry a G19.
I don't want to like Glocks, but my experience with those G19s was very favorable. I haven't researched prices all that much, but I did research G19s a while back, in comparison with the SR9, SR9C, M&P9 and 9C, etc. $499 sounds like a pretty decent price and if you don't like it, I wouldn't expect you to have much trouble selling it. Honestly, I doubt you'd even take much of a loss. The used Glocks that I saw seemed to have held their value pretty well.
A gunfight is not the time to learn new skills.
If you ever have a real need for more than a couple of magazines, your problem is not a shortage of magazines. It's a shortage of people on your side of the argument. -- Art Eatman