Can someone explain what features the USB connection will allow? Can it be used to send digital music and videos from a PC to the 997? Send digital music and video from the 997 to the PC? Do firmware updates to the 997?

We know that it will allow output of EQ curves (before and after) from the Trinnov processing. That's the only thing we've seen officially confirmed. If we assume that it will also be comparable to what the 990's USB port does, it would also support firmware updates and let the 997 act as an external sound card for a PC. The 990's USB input is limited to PCM stereo (no DD or DTS bitstreams). I seriously doubt that it would support video, and I doubt it would allow the 997 to output audio via USB.

USB turntable input for phono?

usb audio output from a pc to the 997 would be a nice feature. it may be better than other methods of sending audio digitally (coax or toslink/fiber) since it offers error correction on the receiving end.

The 990's user's manual, available via the Outlaw Audio products page gives a basic premise of the USB port functionality, which most 990 users expect will be part of the 997 features.

I don't claim to have any knowledge of the 997, but it wouldn't surprise me if the Trinnov output was nothing more than an image sent to a storage device (i.e. a USB thumb drive) attached to the 997. SMS-1 users like myself have long relied on digital cameras to capture the graphical output of our hard work for posterity, so a simple image grab is definitely a useful feature. Since in addition to the image I usually take notes of settings, etc., any other output will be great too. Heck, text-only output will be fine with me, I still have a digital camera.
;-)