Oddly enough, I can report that everything is... working. Really.
Core i7 (2.66 GHz) MacBook Pro 15"
4GB RAM, NVIDIA GeForce GT 330M
Running 10.6.4 in 32-bit mode
Using the Diamond BVU195 USB-DVI adapter (attached to the MBP via a Belkin USB hub)
DisplayLink 1.6 Beta 2 Driver installed
On initial install, I got the blue horizontal bands at startup, but turned off the auto-switching video option in Energy Saver Preferences, and all seems well. I have two Dell 24"s attached to the MBP -- one through the Mini DisplayPort and one through the adapter. There's a tiny perceptible lag on the DisplayLink monitor, but more than acceptable for Photoshop palettes.
So, for the moment, I have no complaints at all.