For those who have never heard of ControlMasters, I highly recommend them. SSH can multiplex multiple sessions (you invoking ssh at the terminal) over a single TCP socket — this feature is called ControlMaster. The first ssh command takes the normal amount of time, but every command after that is just ~a round-trip. No slow asymmetric key exchange. If you close all your connections, there a (configurable) timeout until the ControlMaster's connection closes.
You can combine this fact with zsh's autocomplete powers, and get pretty-close-to-instant (on a good connection) tab-completion of directories on the remote server, which is extremely nice when trying to scp something, as you can tab complete the paths in that command.
(It also saves a few PIDs on the server, as a single sshd child deals with all your connections.)
> You can combine this fact with zsh's autocomplete powers,
I found that recent versions of SSH have begun hashing `~/.ssh/known_hosts` which nerfed zsh autocomplete pretty badly. You need to set "HashKnownHosts no" in `~/.ssh/config`. The SSH change was made to prevent a key compromise from giving an attacker a ready-made list of vulnerable next targets.
Bash history rotates (or can be managed, which a lot of people do), whereas known_hosts will have every server you ever accessed and is rarely ever touched.
You can combine this fact with zsh's autocomplete powers, and get pretty-close-to-instant (on a good connection) tab-completion of directories on the remote server, which is extremely nice when trying to scp something, as you can tab complete the paths in that command.
(It also saves a few PIDs on the server, as a single sshd child deals with all your connections.)