Userspace Camera Drivers

The pwcx debate has made me wonder why USB camera drivers are in the kernel. I can think of two reasons:
1) libusb doesn't support isochronous transactions.
2) V4L is the only generally accepted video capture API.

IEEE1394 cameras took a different path:
1) An isochronous transaction manager for kernel space -
http://www.linux1394.org/video1394.php
2) A userspace library to access the cameras -
http://sourceforge.net/projects/libdc1394/

Problem 1 may be fixed by Mac Cody's code, though I've not tried this myself yet:
http://sourceforge.net/mailarchive/message.php?msg_id=8816704

Is there an existing library that would handle problem 2? Gstreamer might do it, but the documentation is much more oriented to media playback than machine vision.

- Adrian Cox
Humboldt Solutions Ltd.