My Ubuntu 8.04 shipped Firefox 3.0.1 today. Unfortunately the Remote Console plugin is marked incompatible with this version.
I could solve this with a simple hack:
I downloaded the plugin (with wget) from https://127.0.0.1:5443/ui/plugin/vmware-vmrc-linux-x64.xpi,
unzipped the xpi,
in install.rdf I modified <em:maxVersion>3.0.0.</em:maxVersion> to <em:maxVersion>3.0.</em:maxVersion>,
zipped everything together into an xpi file
and installed this intomy Firefox 3.0.1
This works fine for me, but VMware should really provide an updated plugin.