The Second Life Knowledgebase now has an article that explains the stat readings and how-to for version 1.7 of the servers:

http://secondlife.com/knowledgebase/article.php?id=091

with a related post here:
http://secondlife.com/knowledgebase/article.php?id=174

This can be handy for gaining visibility into the various areas of performance troubles (your net connection, your computer, sim scripts, sim avi load, and others), but it won't tell you where CPU-hogging scripts are or who owns them.