So, I've got parcel with scanner in August, but unfortunately had no spare time for hacking, I only coded driver stub and read datasheet from AuthenTec.
So, in September/October I've spent few (5-6?) nights hacking on this driver, and finally got it working on my AES2550. Image quality is much better then on my AES2501. Driver lacks crypto features for AES2810 and external flash support for both devices. Anyway, libfprint has no external flash API yet, so there's some space for hacking :)
As usual, code is on my github page, branch aes2550-v2. Some testing is appreciated :)
P.S. Thanks to AuthenTec for opened specs and provided hardware! AuthenTec rocks!
Update: driver was merged into upstream, so you can use upstream libfprint repo