It’s in beta, don’t nobody panic.
The last 3 releases of WP, I’ve made troubleshooting posts about what to do, what plugins are going to barf, and so on. This time, there really doesn’t seem as much to worry about. Of course, having said that, everything will die in a fire. Actually, though, I haven’t made a list of things yet, because there’s nothing to list. I’ve not run into any stand out ‘Oh shits!’ and the forums are remarkably quiet. So. If you’ve got stupid problems, or found you have to edit themes/plugins, please reply and let me know! I’ll get on it.
So here’s some of the cool new stuff:
Twitter was added to oEmbeds — This should just work out of the box, but if you have a plugin (like Blackbird Pie), you may want to disable it before upgrading.
RPC-XML support for Custom Post-Types.
Admin Toolbar To The Top! Click on any blank space in the admin bar and you go to the top of the page. (It’s the toolbar, damn it, I know this!)
Sexier Theme Options. Have you ever wanted to see what the changes did to your theme on the fly? Go to WP Admin > Themes and click on Customize Theme to get a quick way to see what you’re tweaking. Not every option is there, nor will every option be added, but this is pretty nice!
You also get that view when you preview a theme.
Of note, Twenty Twelve and Favicons got punted to 3.5.
Edited to add…