That's why I don't like the automatic updates but don't like my system freaking out because I turned them off.
I neither want nor need SP4, and it may dl automatically at some point, but I did have the option to dl IE8 myself which I did but let it sit there and wait to see if any problems reported, then installed it. I hope that will be the case with SP4. So I need to figure out what they want to install before I let it go ahead, and may have to get some help with figuring out where to look on my computer and how to tell what it is.
I did get hit with that blaster virus, but that was a long time back and checked the updates more frequently after that. But when I saw SP3, I'm like you, wait and see if people start reporting problems. Now at some point they forced me into auto updates; I did NOT turn them on.
SP3 is purdy...we were quite pleased with it. Not messing with a good thing tho.