I've had sp2 installed on my laptop since the RTM version was released. Really, I've not had any problems that I couldn't quickly work out. I'd say the most important thing is to check for updates to all your system utility programs (AV, firewall) before installing. I knew that NAV would have problems, so I used liveupdate to update the core program. Also, my version of ZA pro wasn't compatible with microsoft's "security center" so windows always wanted to bitch at me for not having a firewall (I turned off the windows firewall). I went ahead and updated to 5.1.11 and I've had no problems. I have the security center disabled now (it's a service) because I just don't need it taking up cycles.

I must say, I highly dislike the new windows firewall. There is no program control, so if I got infected by a worm, there would be no way for me to stop it from getting out to other computers. Also, if somehow a trojan got in, it would be able to open a door without me knowing. Also, why would the windows help center need to access the internet? Or windows explorer? So that's why I use ZA.

I've also read that nmap and other network tools no longer work, but I've not tried to use any of them since the update.

Really, I've not used any of the new updates (AFAIK). I've turned off my WAP so I've not played with the new wireless wizard. Also, I use Firefox so I've not used the new version of IE.

In summary, check for updates, be ready to play around with stuff for 15 mins, and watch for bigger problems down the road.