I have been reviewing some of the enhancements and the idea of a Compatibility View concept just makes me cringe. This concept basically lets you view the current site as if your browser were IE 7. Apparently the IE 8 team made a choice that would effectively break some sites, Joel Spolsky goes into some great details about the issue (somewhat verbose but very important for web developers).
I do like the the InPrivate browsing, the idea of not having to necessarily delete my cookies and offline content after purchasing and browsing the web is appealing. Key loggers aside this does make it much safer for people who use public PCs in public locations.
With that said, I am not sure if I really have a choice about downloading this, it will be my professional problem soon enough.