I had one of those weird bugs on my windows phone 7 where the phone would report an error 800C0069 and would fail to synchronize on the primary account. This can be a major headache as there is no way to remove the primary account on Windows Phone 7 without...
One of the most annoying things I have found about Vista is the file explorer. It constantly changes the views of folders and way too often sets the columns in a folder as if the folder contains photos when it doesn't. To me that is really disappointing...