Well, one great thing about the Mac that became apparent today - it's got all the powerful Unix tools under the hood.
I was trying to diagnose an SMTP problem today and needed to watch live SMTP connections. First I found a Perl script that sends an SMTP message with a Verbose option. Perl is already installed on the Macbook, so it worked straight away. The problem seemed to be timing related, so instead of writing ./smtp-client.pl I wrote time ./smtp-client.pl and I could get a measurement of how long the message transaction took. Then I needed to send a really big text file as another test; so I just typed uuencode bigfile.ppt to generate a 1Mb text file.