Thanks for the great plugin guys!
I just switched over to subversive from subclipse and tried installing the 0.7.4 subversive plugin and it wasn't working, so I took a look to see if I could find the problem.
It appears org.eclipse.externaltools.svn.subversive/META-INF/MANIFEST.MF requires the incorrect version of org.eclipse.externaltools.
On line 8 (http://beyondcvs.cvs.sourceforge.net/beyondcvs/org.eclipse.externaltools.svn.subversive/META-INF/MANIFEST.MF?view=markup) it can be seen that it is requiring version 0.7.3. The current version is 0.7.4.
I changed that line to require 0.7.4 rather than 0.7.3 in my local version and the plugin appears to be working correctly.