PROs:
-every 1911 gun that I've used a FLGR in, I note a reduction in muzzle flip and a reduction in time to reaquire my sight
-the extra weight in the front of the gun does a faster target recovery, reduce a bit of recoil
-improve reliability and increased spring life (maybe, but I'm not sure about this)
-also pistols were smoother to hand cycle after installation of a full length guiderod
CONs: none