I know other Solaris people who have reported unthinkably slow
connections using SSH, though neither I nor they could figure out why.
Point being it is possibly a problem only on the Solaris host and not
necessarily unique ;-)
The one Solaris machine I use, I cannot stand to SSH into it because it
will occasionally suddenly slow to a crawl. This is during the day and
nothing else is happening on the machine (although I don't know about
network usage). The admins attribute this to a bug in the Solaris SSH and
told me to just telnet in.