According to this info over at the Reg, the new BitLocker Drive Encryption's going to make it much more difficult to dual-boot your PC with Linux & Vista.

"This encryption technology also has the effect of frustrating the exchange of data needed in a dual boot system. 'You could look at BitLocker as anti-Linux because it frustrates dual boot,' Schneier told El Reg. Schneier said Vista will bring forward security improvements, but cautioned that technical advances are less important than improvements in how technology is presented to users."