I've downloaded the service pack but have not yet installed it. Today I stumbled over a post on the ESRI forums where problems with reference scale and labeling are discussed. Apparently, this is now a known bug (NIM067942).
Normally, I would install a Service Pack to correct existing issues and to possibly improve performance but it seems that new bug(s) were introduced as well. This particular bug could potentially be a nuisance.
How buggy is it? Will I benefit from installing it? What are your experiences with this particular service pack?