At any respectable pistol range and a bit beyond, the Glock 20 is fairly accurate. I have the standard frame and not the SF. I do not have very large hands and I have full coverage on the grip and the trigger is not a stretch. I think some people with smaller hands may be challenged.
The stock sights work well for daytime shooting, however, I will want night sights before I would feel very comfortable at night.
One great feature of the Glock 20 is that by simply changing the barrel with a conversion barrel, it handles 10mm, 40S&W, 357 SIG and 9x25. The 40S&W and 357 SIG does not require a magazine change. I do not know about the 9x25.
Recoil is not bad, but I have been firing hot loads for over 30 years. It's not like firing hot loads in a scandium J-frame.
The Glock 20 really endears itself once you have it by your side. I have not had problems finding ammo, but I have not tried to get ammo for it on the road.