Base types, Collections, Diagnostics, IO, RegEx…
I propped the character class subtraction specification up on the BCL website:
http://www.gotdotnet.com/team/clr/bcl/TechArticles/techarticles/Specs/Regex/CharacterClassSubtraction.doc
This feature will be one of the many enhancements we make to Whidbey, so keep an eye out for it in Beta1.
Any feedback on the specification is appreciated!