Today was the day, I could finally upgrade to the stable release of WordPress 2.8. I went to my admin and clicked the button to automatically upgrade, and whoosh there it went.
And then it stopped.
I got nothing but blank pages, the so called white screen of death (similar to the blue screen of death as in NOTHING WORKS!). The site worked, but that was about it.
Then I went searching online for possible solutions and with a simple click I found one of them. Disabling all your plugins and then enabling them one by one to see who the culprit was.
Did that. and now everything seems to be in working order.
I recently upgraded as well. It seems that sometimes the little things are the best solutions.
I had the same issue (except for me, white screen of death meant absolutely no site, no admin system, nothing) with 2.9 and 2.9.1. I simply renamed my plugins folder and could then login to the site, reactivated and everything was fine.