It seems that upgrading tinyMCE to latest version fixes the problems in IE9.
Download latest 3.4.7 version and replace the old files on your FTP (don't forget to backup the old one).
You don't need to upload all plug-ins, just following ones:
After overwriting files, clean your browser cache, refresh your page and WYSIWIG editor should fully work in your browser.
Regarding the FF/Chrome/Safari/IE or Opera debate, well everybody have the right to choose their own preferred apps.
As for me, I would burn IE in eternal flames of hell (no matter the version) never to be released again