The problem I've observed is that if an AFP client abnormally looses
their connection to the server (like a brief network outage somewhere
between the client and the server), the server won't allow any new
connections. Trying to unload and reload AFPTCP hangs the server, and
the only way to get it back is to power cycle it, or break into the
debugger and down it.

Has anyone else observed this behavior?

I realize the official answer is to upgrade to SP5, but frankly I'm a
bit nervous about it until I hear more feedback on SP5. It is sounding
mostly good, but then there are still reports of users having memory
problems with it.