I originally downloaded WordPress 2.0 a few days ago befor ehte official release announcement on the blog. I upgraded a test blog to 2.0 (http://css.boltsmag.com ) to test things out - various features, design and what not - and had no trouble... Everything worked great.
Last night I installed 2.0 to a new site that is using some of the exact same content from the test site... First off, the new site will not allow me to disable rich-text/WYSIWYG editing. I was working on a mailing form-field page and the form field is not displaying properly. The majority of the form works up until I get to the textarea for the form... Things get awkward and the last several lines of the form are placed in the text area (these lines are for submitting the form and resetting the form)...
You can view what is going on here:
http://zimmermann2006.com/contact-carl/
I have this same code running (with variations) on other WordPress sites and have no problems. The testing site has the form working exactly as it should be under 2.0... I'm starting to think it's something with the Rich Text editor getting confused -- and yet going through options / Write and disabling rich text editing is not working (unchecked all the checkboxes and still I am forced to edit in rich text).