I decided to give the newer version of Tor a try today. It took a few more steps than I was expecting. I ended up having to move the existing /var/lib/tor directory and recreating it with the proper ownership (debian-top:debian-tor) and permissions (0700). After that everything worked fine. It seems like something about the existing configuration in the 0.1.2 branch prevents the 0.2.x branch from working after upgrading. Of course, if I decide to go back to the stable version I expect I may want to restore the previous version of the directory. But for now the 0.2.20 version seems to be running pretty well.