If you use WordPress, I advise against upgrading to version 2.8. I attempted to do so to this site this evening (via Subversion), and everything appeared to go smoothly. Unfortunately, upon logging in to my admin panel, I noted that everything was broken. The external site still performed as expected, but I couldn't get around in the admin area.
Zero steps forward, twenty steps back.
Maybe others will have better luck than I did. I have since reverted back to 2.7.1 for the time being, though my database may now be corrupt. If you notice anything funky around this site, please, please, please let me know.