I'm working the same way and haven't come across any issues yet. Fingers crossed!
Navarro Parker wrote:
I still need to use AE CS4 for some plug-ins that haven't made the jump to 64-bit. Are there any features or problems using Photoshop and Illustrator CS5 created files?
Not that I know. Luckily, AE doesn't dig deep into these files and only uses data it can really understand and has understood for a few versions. I would advise against any crazy experiments with Photoshop 3D, though. This seems to be busted in a variety of ways with back and forward compatibility within PS itself and then in turn affecting AE.