I had some issues at first. Zonealarm was bluescreening my machine, a cdsys file kept me from installing at first. Also, my old Ad-Aware AdWatch did not uninstall when I installed the SE version, and that gave startup errors.
Now I cleaned up my old problems that I had before upgrading, and have gotten ZA Pro 5.011 and SAV 9.0.1100 CE to install AND talk to the new security center so I do not have to use the built-in firewall and antivirus.
The problem is that eventually you will not be able to patch serious flaws with a base SP1, and will have to install SP2 to build off of. Also, for those who like to slipstream, the new hotfixes (incl the last 4 for SP1) can be integrated with the /integrate switch, so no more scripted install CDs (except for IE and MSDE patches).
Overall, I am stable and happy with SP2 now.