Add me to the list. My Duemilanove has/had no issues. Just got an Uno, and I'm seeing all of the same things. Uploads are now through ACM instead of USB, Tools menu is very sluggish. However, repeating does not ever seem to push the program through. The TX button seems to be permanently lit, and after each try, I have to delete the lock file from /var/lock and reselect ACM from Tools.
I'm running 10.04 as well. Suggestions would be very much appreciated!