"Thanks for the information guys. I guess what I was going for when asking this question was personal experience, but no one seems to have ever actually done it themselves (as unterhausen pointed out), so I'm just getting a lot of speculation/guesses/opinion, which is totally cool, because that's all you can give someone when you haven't actually tried it yourself."
It's a little more than that in my case since I have spent at least 5 years trying to build quality bikes in the home shop environment with redneck methods. So I have tried everything from stick welding to.. OK except MIG. For two reasons as regards the latter, have basically had my fun doing it with stick, and I think in individual hands MIG is the least suited.
Also I would point out that while I enjoy speculating as much as the next person, the stuff about cold starts is plain fact, and is why MIG is allowed on certain jobs, and less so on high end structural stuff.
"But the real issue about asking this question in this forum is that nobody that posts here on a regular basis uses MIG on bike frames."
Another issue that bothers me even more is that while these newbie(s are welcome) questions always go into their pant size and what their girlfriend ate for breakfast details, they very rarely give one any real info on what the person is trying to do. They spend a lot of time describing them, and not the job. At least in this case he mentioned tubbing wall size. So OK, I'm sure you can weld with MIG a bike frame with 1/8" walls. In fact, it is pretty obvious from looking at factory stuff that crap welding works fine even with the 35-65 thou tubing welding. The problem is since we don't know the actual details it is hard to speculate and everyone is forced off onto tangents about what is good for the craft or what they did on the summer vacation.
Hey PAPA did they call it GMAW back in the 70s. I hate it when some kind of industry body changes all the letters and adds more without really adding anything to the general understanding. Congrats on the certs!