My Glock 20 is box stock and has functioned perfectly for about 3 years now. 100% reliability after 5000-6000 rounds and accuracy on par with midlevel custom 1911's. I had considered a Jarvis or Briley barrel a while back, but didnt want to lose the extra velocity I'm gettting from the polygonal rifleing (no its not marketing BS). I have been told to replace the recoil spring with a Wolf model since I shoot alot of full-house loads, but the stock one works fine so far. When and if it starts to wear out I'll replace it with a Wolf or similar.
I got tired of my Glock looking exactly like every other Glock out there, but didnt want to mess it up with alot of ugly aftermarket Aro-tek stuff so brushed the slide release lever to a nice "brushed aluminum" finish leaving the groved black. ende up looking pretty nice. Everyone asks were to get one.
I reload for mine also, but still hav ethe same barrel. No problems thus far with out 40% of the ammo fired through it reloaded. Glock will do fine with reloads, they just require you to be extra carefull. Hot reloads get brand new cases that are discarded after fireing. Medium power reloads get new cases that I reload only twice more. Interestingly enough my medium power reloads are almost the same powerlevel as Silvertips and are no were near max load.
BTW...I dont use the lazer anymore since its getting cool enough to wear a jacket and carry my Glock 20 again. the lazer makes for a very fun range toy when I'm not carrying.