At "my" IDPA club/range, Glocks are the seeming majority in Stock Service Pistol, and fare well. There are other very good shooters using their (duty) Beretta's and Sigs also. The compact Glocks seem to be the favorite in the Backup gun matches. I see frequent posts on Glock Talk about guys shooting IPSC limited with their Glocks, and doing well, even against 1911's.
I've been shooting SSP with my G22, and know the biggest limitation is my own ability. There is an expert class shooter, who shoots mostly his 1911, but sometimes a G19. His times are surprisingly close with each gun. Although the 1911 trigger clearly has no equal, the Glock trigger can be mastered. I heard recently that Rob Leatham got a G35, and is supposed to like it a lot. FWIW. I covet a G34.
------------------------
So many guns, so little money and ammo.