Just got the email. I don't know what to upgrade first. I think I'll do a fresh install of a domain that I have been holding for just this occasion. I'm all giddy inside Check out the Video: http://wordpress.tv/2010/06/17/introducing-wordpress-3-0/
Just did a fresh install with the MU functionality. It was pretty painless. It only took a little longer because I was exited and skipped a step or 2. Found a nice tutorial on making the needed file edits: http://journalxtra.com/2010/06/activating-wordpress-3-0-multi-site-formerly-multi-user-mu/
So excited! It will be nice to have WP MU bought into the fold. I had a quick skim over the main points this morning, but it looks like a decent upgrade. Some of the new code looks handy, like the WP_Log_In() hook or whatever it is. And they moved from Kubric to the new Twenty Ten as the default theme. It will be interesting to see what other differences there are!
Upgrade on my websites went smoothly, but on some more customized themes there was a problem with menus, because new wordpress menu options have problem with theme custom menu. So I had to downgrade few of them. I'll wait some time and upgrade them later when there will hopefully also be theme upgrades for 3.0 version.
Well, 3.0 is working like a charm.. but some plugins will stop working thats all.. but you can get updated versions of the plugins soon... Thanks.
I agree with extremephp, the upgrade went well, and it works way faster. I don't really like the grey top bar in admin page though, but soon i will get used to it Do upgrade as it runs faster, and more secure.