This TinyMCE editor works poorly with Firefox 2.0.
When I press enter, I have no idea how many vertical spaces will be inserted. Often, multiple vertical spaces show up in the editor, but no vertical spaces show up when I post.
If I switch to source code view and then back to WYSIWYG view, the TinyMCE window no longer fits in its container, causing certain features to be unavailable. Furthermore, scrolling up and down after doing this often junk or whitespace to full up on the TinyMCE area instead of the actual text.
Oftentimes TinyMCE is unable to boldface or unboldface my text when I click the B icon, but if I hit ctrl-B, the boldface toggle is successful (albeit the Bookmarks window shows up).
Overall, I feel that either the TinyMCE product or its implementation in WordPress is just downright awful.