The new Time Capsule peripheral is an interesting beast: an Airport Extreme with a Frankenstein complex, with an onboard drive for backup storage. What else can you do with that space? According to Apple reps at the booth, the drive appears just as a wireless disk would appear with the original AE base, so you can in fact put other data on there besides the Time Machine backups. Since TM backups tend to grow to consume all available space, partitioning the Time Capsule drive might be a good idea if you can do it in advance. We'll try to get hands-on with the Time Capsule utility later today to verify that you can split it up.

As the Time Capsule is otherwise identical to an Airport base, you can hang printers or USB drives off the unit and share those as you would with the older gear.

Update: A further conversation at the Apple booth leads me to believe that you will not be able to partition the drive on the Time Capsule. If your purchase decisions are contingent on this capability, please wait until I can get a solid answer from the product manager at Apple on this. You could conceivably 'reserve' space on the TC by creating a disk image to hold your files, but I wouldn't recommend that unless you absolutely have to do it. A couple of contrary reports are saying that you cannot store other files on the TC drive, but everyone I've talked to says that it does mount as a regular wireless disk and you can write to it if needed.

Some other concerns:

"Can I connect the Time Capsule as an external USB drive, directly to my Mac?" No, that functionality isn't in the Airport Extreme and I wouldn't expect it to be in the TC -- however, with gigabit Ethernet you can transfer data faster than USB anyway. Note that I said AS a USB drive, not TO a USB drive -- the Airport feature of external drives connected to the TC is still there, but the external drives aren't valid backup targets.

"Can I stream directly from a Time Capsule to my Apple TV?" Probably not; while you can store an iTunes library on a wireless disk, you still need iTunes to mediate between the storage and the Apple TV.

"If the Time Capsule is the same as an Airport, when will Apple enable Time Machine backups to external USB disks via the Airport?" Could be never. It's been suggested by some (including some of our own) that the combination of the wireless bridge and the USB storage bridge is simply too latency-prone and laggy to provide the needed performance for Time Machine, and that the SATA internal on the Time Capsule is integrated and speedier to allow TM to behave as expected. With no SATA bridge on the Airport Extreme, and no forecast on a fix for the write caching issues, don't count on official support for wireless backups via that hardware.

"Can I use USB wireless networking devices (Sprint or Verizon EVDO) as broadband connections for Time Capsule?" Nope, not directly connected to the TC -- not a feature of the Airport.