The Glock 19 works for me, but just not as well as my old S&W 3913. The Glock is only slightly larger (height is the same, length is shy of 1/2" more, thickness is shy of 1/8" more) than the 3913 and really no harder to conceal.

Glock 19s and Glock 17s both seem to work, pretty much all the time and as others have said, they are easy to keep running and repair in the rare event of parts breakage.

Having made those observations, I still carry the 3913, despite the Glock's capacity advantage of seven rounds (16 vs 9). A friend who was just back from Afghanistan wanted to try a 'standards' marksmanship test someone had showed him - shoot three rounds into a 3" circle at varying distances and positions out to 25 yards. We both came pretty close with the Glocks, but I 'cleaned' it with my old 3913.

The Glock just never seems to 'blind point' reliably for me; everything is fine for five or six repetitions, then, for no apparent reason, the sights are not aligned. The little Smith is 100% for me, just about in the same class as the Single Action Army at eye level. As others have said, shot placement is everything - with the Glock, my shot placement is not quite as precise as it is with the 3913. I would probably carry the Glock 19 if the S&W 3913 did not exist...