Let's breathe some new life into this one -
It's not, at all, uncommon for an experienced Glock pistolero to use an assortment of different recoil springs. I keep 3 different weights for each of the Glocks I own. -1# down, standard issue, and +1# up. This accomplishes several things for me:
1. I'm able to increase or decrease the amount of perceived (controllable) recoil I experience. A fast pistolero, who's concerned about his split times, will tend to go lower on recoil spring weight - Often significantly lower than standard.
Why? Because his slide will travel faster, his muzzle will flip less, and his front sight will be more quickly recovered.
2. Most pistol shooters will opt for a heavier recoil spring in order to experience a different, but similar, result. The split time between shots will be longer; and the muzzle rise will be greater; however, the actual recoil impulse, itself, will seem more manageable.
There's, also, the matter of what brand of ammunition you are using? If you're getting your ammo from Wal-Mart a -1# spring might be the most appropriate to use. If you're using Israeli or European ammo, then, using a heavier recoil spring is going to be a lot easier on the gun.
Recently, it's amused me to notice that one of the common, 'quick fixes' for the feeding problems with Glock's new 4th generation pistols is to recommend going significantly lighter on the recoil spring.
I've seen recommendations from knowledgeable Glock gunmen as low as -5#'s. (Yeah! I guess that would cycle anybody's pistol, huh.)