Vista is released to consumers tomorrow...
I've been using Vista for two months now and it has been nothing but a pain. It has actually slowed my rate of work by virtue of being slow, unresponsive, and needlessly verbose.
Today I ran a Cygwin script which created some text files. Now I can't get the permissions on the directories will not allow me to remove them, it sends me through numerous UAC dialogs asking for permission and then it throws up an error message with a cryptic hex value. Even editing file and directory permissions fails to alleviate the problem.
It's not just a new problem encountered day to day, it is a problem that slows you down. Installing and executing software is massively slower, I guess due to some security changes. It is all the small things that add up to a big annoyance as there is not one thing that is excessively bad (although UAC is close to that).
The best problem I have on Windows Vista is that I can't reboot because it breaks my C++ compilation in Visual Studio 2005. Sounds mad, but it is completely true, the precompiled header or something causes an internal compiler error when trying an incremental build even just changing a single .CPP file. Unfortunately I can find no relevant documentation on this problem.