The main problem I'd see is training users to get that initial trust phase correct. Too many wouldn't try to parse the info given and just click Trust regardless (or run away from every site with the warning).
The same way, except SSH is generally used for a small number of hosts that the user itself (or their organisation) controls, so there's some chance for out-of-band verification.
Not if you are doing SSH right... That "fingerprint validation" message you get the first time you connection to a SSH host: you should be verifying that against a copy received through another (preferably secure of course) channel, not just blindly trusting the first fingerprint you are shown.
The main problem I'd see is training users to get that initial trust phase correct. Too many wouldn't try to parse the info given and just click Trust regardless (or run away from every site with the warning).