The conversion script isn't perfect and does fail on complex CVS arrangements or where there is extensive history to migate. However it appears above that Martin has already tried the script out, with success.
I'd still like to hear from Jim, as I don't believe all serious problems were identified by eyeball at once. That said, the Python project has made relatively very little use of complex (for CVS) concepts like branching, but in Zopeland it wasn't unusual, over long stretches, for someone to make a new branch every day.
Ah, before I forget, "single repository" has worked very well for Zope (which includes top-level Zope2, Zope3, ZODB, ZConfig, zdaemon, ... projects):
Long URLs don't really get in the way in practice (rarely a need to type one after initial checkout; even "svn switch" is usually just a tail-end cmdline edit starting from a copy+paste of "svn info" output).