I upgraded Visual Studio 2003 to SP1 a few days ago and I am going to uninstall it right after these lines are written. I had more trouble with SP1 during the last few days than with the unpatched version ever before. My experience with SP1 is that:

• It breaks the highlighter. Comments blocks seem to be a problem now.
• It makes the IDE crash very often. Your unsaved code is lost!
• It produces a lot of bullshit link errors. Rebuild the very same code and they are gone.

I even got Unicode garbage from reading an Ansi file using fread once, no joke. Now it's enough: The installation has been a pain already and now I'll kick it off my disk. I highly recommend to not install SP1!