I'm using it on one machine and I'm going to go back to SP1.

The new "security" is a PITA. This probably bothers developers more than anyone else, but if I see that stupid bar at the top of a web page about how IE is protecting me from myself one more time (and the associated cascade of "are you sure"s), I'm going to break something.

The Bluetooth stack, near as I can tell, has completely broken all useful functionality. For example, go browse your mobile phone and transfer some images, sounds, videos, whatever. Oh, wait, you can't because there is no way to do it. You have to pick the images one at a time and send them from the phone. Compare this to the Bluetooth stack that came with my Logitech keyboard/mouse: right-click the icon, Quick Connect > File Transfer > Name of device and there's a window with all your files.

Pop-up blocker seems redundant with the Google Toolbar, and now that I'm accustomed to it I have no interest in getting rid of it.