I backed up my home directory, deleted Intrepid Ibex and went back to the previous version, Hardy Heron. (note--these are versions of Ubuntu Linux) The sound problems were maddening, and troubleshooting took too much time because the problems didn't appear until several hours of use. I usually had to restart Firefox to play any flash with sound. I'd lost the ability to control keyboard repeat rate, and there was a keyboard issue I'd fixed before that came back, where the computer would occasionally drop a key event--either it would ignore the key entirely, or it would not realize I'd released it and would go into repeat until I hit another key. I would also get maddening keyboard lag in some web forms--the display might be 2 words behind my typing. Dual screens sort of worked with almost no trouble, but they don't work right--Glitches in the primary display, and it kept wanting to move my toolbars to the second monitor.
One of the really nice things about Linux is the home folder. Most of my customizations go in the home folder, so by making a copy to an external drive (make sure you also back up hidden files) I could reinstall the older version, then when I copy my home folder back, I wind up with most everything configured the same way I had it before. Even third party applications kept their settings.
I may try a clean install of Intrepid sometime in the future, but as a second OS rather than an upgrade.