I've never left the default password in place (until 1.1.3 jb). I don't leave SSH enabled all of the time either.
When DLing BSD it specifically warns against changing the password (with passwd) or else you will face a constantly rebooting springboard.
Now I have to rely on disabling SSH. The problem with that is I have no idea when a problem might surface and if SSH isn't on my only option is restore, or try to get by with iBrickr.
So I use BossPrefs to disable SSH. HOWEVER, I turned on the option to have SSH enabled after a reboot. This means I can turn SSH back on just by rebooting my iPhone. The drawback is that I have to remember to disable it when rebooting for another reason.
SSH has bailed me out many times prior to 1.1.3 (usually due to M68AP.plist). I have already needed it once under 1.1.3 too (yep, the rebooting springboard issue--apparently caused by more than just using passwd).
There are other ways to change the password other than passwd, but I just haven't gotten around to doing it yet.