Potentially this is old news, but via Raymond Chen we learn of this page:
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnlong/html...
Which talks about Vistas application compatibility. Interesting points that stand out:
* They are dropping WinHelp and CHM support. You'll have to install it from their website for it to work (my first thought: wtf?)
* IsBadReadPtr/IsBadWritePtr are now "banned". I wonder what that means. Presumably it just means they don't use them internally for the APIs anymore.
* Windows will now silently fail to modify certain protected system files even if you're the administrator (basically the STATUS_ACCESS_DENIED error is suppressed to stop installers tripping up).
* They dropped D3D RM. Not many apps use this but I think at least my fathers sailing game does.
So there we have it - this appears to be the first release in which they simply started dropping APIs.