I, for myself. will wait till later in the year. That seems to be the overall suggestion by the tech community 'advice folks'. They all say it needs to be done, but with known issues, and maybe more importantly, the unknown ones, the little bugs and all, that best advice is to hold off for some weeks, maybe a month or two. I am heeding their advice.
I know of several folks, some here on the DIS, who have updated and had no problems. I know of several who did beta work (I, personally, would not beta on anything that big) and had no real problems. I have not heard of anyone who has updated and had problems. But I'll wait a bit, for my own machines.
Additionally, if you are diligent in your other MS updates, especially criticals (there was another yesterday, regarding jpg's), diligent with your anti-virus, spyware, firewall updates, at least weekly (mine are daily or constant), SP2 does not bring a whole lot new to the table.
Here is a
link that may point out some issues. I did order the CD, just to have in my CD file and when I decide to update, will use the CD.