SpaceFM works perfectly.
Download it from here http://ignorantguru.github.com/spacefm/
, then install it with GDebi.
Upon installation in Mate, I was pleasantly surpised to see it automatically installed as the "preferred" file manager in the system/preferences/preferred applications.
For anyone who currently misses the "custom actions" of Nautilius in Caja, and who would want a nice speed increase in a file manager, SpaceFM allows command line actions to be very quickly and easily defined (such as shred or wipe or md5sum, etc), as well as offers a nice selection of plug-ins from the site.
At least until Caja matures a little bit more in functions