(1) No matter what people's experiences have been, until your particular flight is boarding and your group is called, and you board will you actually know what will happen, even if 99% of the people responding have had nothing but ample space; and
(2) Hasn't this already been hashed and rehashed in at least a couple of other airline-specific threads?

The simple fact is that if you have "compliant bags" and you want to insure the fit, you must insure that you are in an earlier boarding group. And that can cost more money. Anecdotal experiences don't help anyone when one must insure space at your time of boarding. If I needed to insure that I had space and I'd have to not take the flight if my hand luggage needed a gate check, I'd not risk this. End of discussion.