So after getting Eclipse 3.5 and Flex Builder Plugin for Windows to work last week, I dug in yesterday to get it working on my Ubuntu system. After reading an invaluable tutorial, I was still getting some odd errors where Eclispe appeared to recognize that Flex Builder was present (it was in the About Box), but I couldn't get any MXML or AS editors to open. Poking in to the directory structure, I found that the $ECLIPSE_HOME/links/com.adobe.flexbuilder.feature.core.link file was incorrect. It appears that Galileo requires the "path=" to be prepended to the path for the core plugin, but Adobe's default install doesn't include that part of the file. After adding "path=" to my link file, it fires up just fine. Still no design mode, but if we keep bugging Adobe about it, they might add it into Flash Builder 4 for Linux.