I notice both you and drtse4 like the tool but only mention what it's advertised to do, and not anything specific about your experience using it over 'ssh -D'. How has using it changed how you would have used 'ssh -D' ?
I suppose the most practical purpose for sshuttle is for shell accounts on a box you don't own, if you need to do random transport-level stuff to remote hosts through an intermediary and you want to use a client on your local host. So basically NMap if your shell doesn't support it and you can't copy-and-run 3rd-party binaries. I'd be interested to see how well sshuttle performs under an intense NMap scan.