I've got a bike with a 105 (5703) triple drivetrain, and it shifts great. My bikes with Tiagra triples have been a little more prone to gimpy front shifting, but it can usually be cleaned up with a little effort.

This is basically why I think I will be OK with 50-34 for riding on the open road. Last night I climbed the hill to my house (which is about 3/8 mile at 8% and 1/8 mile at 16%) with the 34-29 combination. The 8% section wasn't bad at all. I wouldn't have lasted much longer than I needed to at 16% but I can only climb a grade like that for so long with any gear before I just get off and walk. Most of the paved climbs I see around here don't spike above 8% for very long. And, of course, 50T is good for cruising on open roads.

That said, the whole reason I started this rant in the commuter forum is that when I'm commuting I'm constantly crossing back and forth over that threshold where the 50T ring isn't really comfortable. Seeing so many response that are some variation of "just use the 50T all the time" doesn't really change how I feel about this. I know some people have more open road on their commute, but I don't think it's typical.