My iMac is behind a satellite internet connection, which is very slow. Rather than using Screen Sharing or Finder's file sharing for Back to My Mac, I often find it easier to use ssh. Until today I didn't know how to connect to a Back To My Mac computer via ssh. It turns out that it's very easy:
ssh -vvv -p 22 hostname.username.members.mac.com.
Where hostname is the name you gave to the machine (i.e. the name that appears in Finder), and username is your .Mac username (i.e. if your email address is steve@mac.com, your .Mac username is steve). Note that there is a "." at the very end of the command -- I've had more consistent success using it that way. You can also try Terminal.app » Shell » New Remote Connection (or press Command-Shift-K) and then look under 'Secure Shell (ssh) for "Discovered Servers"'.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20080428132615192