I recently bought the new AEBS. I have a 500GB Lacie Porsche USB drive and an HP Laserjet 1200 connected via a D-Link 7 port USB 2.0 hub plugged into the AEBS. The only problem I've had is that both the printer and the hard drive have to be powered on before the power to the AEBS is powered on (or plugged into it). I haven't been able to find out why, but it isn't a problem unless the power goes out. Then all the power comes on to all devices at once and I usually have to unplug the power on the AEBS and then both devices work fine.
I haven't tried multiple printers, but I have heard some printers don't work. Also, from the research I've done, it's better to have the HD's formatted HFS+ (some say not journaled, but mine is). There is also has been a problem with some of the 1TB drives in that the software RAID the drive uses confuses the AEBS and it doesn't see the drive as one drive. Don't know if this is fixed with the 7.1.1 update or not.
FYI, currently the AEBS does not power down hard drives when not in use, so the drives will run constantly.
Check the apple official discussion group, there's a lot more information there than here that I've found
