In connecting to a local server, my ssh command would take about 20 seconds to complete. Non-Macintosh clients would not see this delay. After searching for the web and slogging through a number of posts that suggested how to change the server to fix ssh delays, I pieced together enough information to find out how to change my client configuration to solve the problem.
The first, and largest cause of delays, was my client and the server working to authenticate me using 'GSSAPI' (Kerberos) authentication. That seemed to be a good 15-18 seconds of the delay. I fixed this problem by adding a configuration file for my user that disabled GSSAPI authentication for the host. The file I added is ~/.ssh/config and I created it to read:
Host -host-name-here- GSSAPIAuthentication no GSSAPIKeyExchange no
That took the delay down to about a second or two. Based on another hint found in this forum, I discovered that the Mac also tries to negotiate with the server through both IPv4 and IPv6 channels. This server doesn't do IPv6 so I changed my ssh config to read:
Host -host-name-here- GSSAPIAuthentication no GSSAPIKeyExchange no AddressFamily inet
[crarko adds: I haven't tested this one.]

