Symantec has just released the first three of six technical research papers evaluating Windows Vista security components.
http://www.symantec.com/enterprise/theme.jsp?themeid=vista_researchThe research papers cover some Vista security mechanisms in-depth
Including some good stuff on Address Space Layout Randomization (ASLR) technology (this was designed to thwart heap overflows and some malware attacks).
Buffer overflow protection in Vista's Visual Studio C++ compiler and an evaluation of how well old XP malware works on Vista.
This is worth looking at.