I also discovered that at least in TrueCrypt 5.1a, you can mount another whole-disk encrypted harddrive as an external or secondary drive and use the option on the System menu in TrueCrypt to “Mount Without Pre-Boot Authentication…” and you can mount that drive as a drive letter, great for transferring data from old drive to new (as I’m doing with XP-to-Vista)! The TrueCrypt folks seem to have thought of everything! No performance hit noticed in Vista after drive encryption, and both Hibernate and Sleep work fine (although Sleep doesn’t prompt for encryption password, it just wakes up instantly, which is to be expected but be aware that Sleep mode does not protect you as much as Hibernate or powering off!).

Also, while hibernation didn’t work at first when they added support for hibernation in 5.1 (it would not resume), it does work now with version 5.1a Beta, which is nice!