Network Traffic Management and Accounting

Yeah I know… a real eye catching title. But anyway. In a recent email with another TR member, the need for traffic monitoring came up. In my situation I use a combination of squid in transparent mode, squid in mandatory proxy, and Wireshark on the servers when I need to see packet data (and on the proxies of course).
Wireshark is easy to set up and use, but I will be learning to interpret data for ever…
Squid is easy to use once its set up, but learning to set it up and install it properly took me a lot of time I do not have anymore, and many people never have.
So what do other people do to track bandwidth usage and traffic types? Any thoughts on commercial products vs open source products? Software vs gateway devices?