I noticed this myself the other day and it has been mentioned on FlyerTalk. AirTran is now charging a premium to preselect rows 12 though 15 of coach. $13 fee now gets you those seats, they also board in zone 1 when in the past these were usually zone 5 or 6. Still no charge if you go through Kayak. If you have already selected seats you can go in and change them to move further forward on the aircraft.
Usually my favorite seat in row 15 is in Boarding Zone 6. It will be nice not having to look for space in the overhead bins.