Well, I can't share the enthusiasm. I have upgraded to the latest VB 4.1.12 + ext. pack + guest additions and not having luck to get the the Internal (USB) card reader to work neither under Windows XP nor Linux Ubuntu. The host is OSX 10.7.3. I have also tried to run guests with 1 CPU only, but no joy.
Anyway, if someone can point me out the direction to get the Internal card reader to work, would be glad to try.