So the judder only begins with the application of the brakes, but stays after releasing the brakes?
Sounds like a sticky brake caliper and/or an uneven rotor - just off the top of my head. I would think that would've been an easy diagnosis by the dealer, so perhaps it's something else. Ask the dealer for an explanation of what they felt the cause was and what they did to correct it, then ask them if they test drove the thing afterward.
As for the wreck, well, that's what insurance is for - at least you're not hurt and heck, it wasn't your car. Still, definitely a lousy day.
2007 Infiniti M35x (wife's)
2006 330 cic ZHP 6sp (current)
2005 Z4 3.0 sp nav x-leather (retired)
2000 323i PP (best car, ever - retired)