There is a certain irony here. We often have readers asking if they will be 'caught' if they exceed the posted limits for carry on items. Then we have readers who report how often flights are delayed due to excessive carry on.
On my US domestic flights, pretty much every time the UA GA's end up checking bags at the gate. They don't even let passengers go down the jetway anymore with those mammoth bags, if they can catch them. Yet even so by the time zone 4 boards there is usually no space left, and many of those passengers also have to gate check. They are also insistent that the personal item is stowed under the seat in front of you, and that winter coats are not put into the bins until boarding is completed.
A few weeks ago I was waiting to board a LH flight from ORD and the LH staff were very dilegent about visually checking bags in the boarding line, pulling people out, measuring and weighing the bags, and refusing them boarding, including the 22 inch bags which are accepted on American flights, but not on LH flights. The DUS/FRA/MUC flights all leave from the same gates and this was quite the show, with people who hadn't read the rules trying to insist that they were fine, and the LH staff refusing to budge.
I know that many of you cannot stand me or my posting style, and I don't really let that bother me.
The rules are the rules for a reason. Not following the rules impacts everyone through delayed flights, or by forcing others to gate check even when they do fall within the rules.
AirTran may have a larger than normal carry on policy, but there is no way that a 25 inch bag will fit wheels in into most overhead bins. 22 inch bags won't fit into a 767 bin wheels first either. Nor will they fit on a 747 UD. Remember too that you will need to lift that 25 inch bag over your head, and you will also need to lift it onto the belt at security. If you cannot lift a 25 inch suitcase over your head at home, don't expect to do it on board the flight.
For the time being, the vast majority of US carriers allow one 22 inch carry on plus one person item, and the 22 inch bag cannot be overfilled. I fully expect that to change very soon in the coming years to conform to worldwide standards. And for those of you flying overseas remember that the international rules apply, which means much smaller carry on, which is often weighed. And frying pans can weigh quite a bit!