I've got avast running and it's fine. I'm really pleased to have an anti virus for linux - we don't get many viruses (yet!) but as more people use linux, it's bound to be more of a problem.
My only query is that the definitions update takes about 15 minutes on dial up. Is it overwriting the whole definitions file? If so, an incremental updater, like you Windows version, would be great.
I've started a thread on
http://www.ubuntuforums.org/ and the first users of avast for linux all seem really pleased.
To get the install to the desktop on ubuntu, the line in your install file has to be preceeded by
sudo !;)