I've been running SP2 since RC1, and have installed on about 10 different PC's and laptops without a single issue. My boot times and general response times have felt slightly better, but I don't have any hard numbers. ;)
While I'm paid to be skeptical of all patches/software, I have to admit my experience with SP2 has been good. From a security standpoint, it's something that has been a long time coming.
The IBM article is a little misleading. IBM SHOULD have been ready for the new port stuff, the beta patch has been out for 8 months or more. The reason this is going to break some apps is not really MS's fault, as not allowing just ANY port access to a box is something that should have been that way since the beginning. SP2 is just going to force programmers to actually think about security for a change. :D