More generally: The ability to back up everything (recorded programs, timers, favorites) so that when a receiver is swapped out you can restore the new one to the previous state.As somebody who has lost recordings and timers due to a failed 622 a way to backup at least the timers. Actually just the timers is fine, have had to rebuild them from memory once, i keep movies i want etc archived on the external drive anyway.
The external hard drive would be a sensible place for the backup. Make it totally automagic both in backing up and restoring.
An "auto archive" function would also be nice. Rather than deleting programs from the internal drive when space is needed for new recordings, the programs could be MOVED to the external.
As others have said, incorporating the content on internal and external drive (both manually moved and automatically archived) into the same browser would make life much nicer too.