Just upgraded this site to WordPress 2.0. I read a bunch of blogs over teh last few days about the upgrade problems, but I didn’t face any. It was smooth as usual.
The only problem I had was with the Akismet plugin. Somehow I ended up with both version 1.11. and 1.12 at the same time. Deleting one fixed the problem.
As a side effect, my previous theme messes up the layout. So I have reverted back to the default layout. Will find time later to fix the theme.
And yes, JBlogEditor works fine with 2.0