Hmm, it feels exactly the other way around to me: working with the DVCS tools while reviewiing a patch allows me to be more productive (e.g., using 'bzr shelve' or the equivalent hg subcommand).
Just try using Subversion for some time again, and you'll see that it is not difficult at all. Start with a clean sandbox, then apply the patch. If you want to go back to the state without patch, revert the sandbox, if you need it again, apply it again. It's really simple.