http://news.yahoo.com/american-favor-passengers-without-roller-151634542.html;_ylt=AhVDI234kBOl8TiYFPUkjJBPXs8F;_ylu=X3oDMTFoNTliYXVwBG1pdANBcnRpY2xlIFRvcFN0b3JpZXMEcG9zAzcEc2VjA01lZGlhU2VjdGlvbkxpc3Q-;_ylg=X3oDMTMxYnVpbnJyBGludGwDdXMEbGFuZwNlbi11cwRwc3RhaWQDM2NiYzgwNjgtNTM3ZC0zZjczLThkN2QtNGZiZTkxMGEwZDcyBHBzdGNhdANob21lfGVkdWNhdGlvbgRwdANzdG9yeXBhZ2U-;_ylv=3

The prior blog post on exactly how large the underseat storage area is just got a bit more relevant.

What potential problems do any of you see with American's plan?

Problem? Other than people arguing with the GA on what fits. You can read real life experiences of this working at FT.
Its a good idea i think, for many reasons. Its not meant to encourage people to travel light though.

The big problem, of course, will be people boarding early with just their personal item putting that personal item in the overhead bin instead of under their seat, so that some of the folks coming on later with legal-sized carryons will be forced to involuntarily gate check their bags. Somehow I don't see the AA flight attendants enforcing the "personal items go under the seat" rule.

I doubt very much that anyone w/o a carry on who does not have elite status is going to board before first class, wheelchairs, babies, etc. etc. -- all with bags, no doubt. If they let the discounted no bagger Ys in before first class and other "elites" there will be hell to pay. If they mix them in with elites there will be hell to pay. So, all in all, I don't see this making any difference to departure times but I do see it being a PITA for GAs.