I upgraded on blog which runs on WP 2.1.1. to WP 2.3 RC1 last night. It is a crazy thing to do, very risky too. But hey, nothing screwed up.
So, I am very confident of upgrading all my blogs to [tag]WP 2.3[/tag] now. For the next few hours, I think that’s what I am going to do with all my blogs. Folks, remember to deactivate all your plugins first and activate them one by one so that you know which plugin is not compatible with WP 2.3.