There's a short article about a change to .ico files for Windows Vista on The Code Project.
Basically, .ico files will allow use of the PNG format, and sizes up to 256x256. It's great that PNG is now supported, but imagine how high the resolution of your screen has to be to have a 256x256 "icon" be a reasonable size... or maybe MS are planning on putting 256x256 icons in the Start menu or something even more crazy?!?