I guess I am very sensative about carry ons. So, if I seem strident about checking them, please, forgive me. But.....I have nearly been decapatated by someone who just HAD to get that "steamer trunk" down from the overhead, been actually whacked in the head by a breifcase that some idiot had to walk back ten rows to get (hear of swimming against the tide) been bruised by others who just had to roll that luggage down the aisle and whacked me in the leg (there were where they belonged, he just swerved). Have seen people who can drag it on but cannot lift it to the overhead, hence the need to hold everything up while someone helps them out. (if you cannot lift it into the overhead, then check it). And, of course we have the people that have to stand in the middle of the jetway (after stopping dead in front of a bunch of people) to pull the handle up on the darn thing. Then.....we have the children, who's parents think the pull along luggage just made for their little darlings is adorable, who love to zig zag along, try to avoid one of those, that is a ton of fun.
i think SWA is making great stride in the carry on department. They are very strict (kudos to them) and their flight attendants are pretty good at letting folks know that they are not going to lift their overweight carry ons into the overhead, you are not going to hold people up by retracing 10 rows to retrieve your luggage, etc. Personally, I cannot wait till they ban anything larger than a briefcase.
Sorry for the rant, but, I do have pretty good reasons to dislike carryons.