>Are y'all looking for instantaneous bandwidth through the interface (kinda
>like the load average?) or a cumulative number?

Cumulative. Instantaneous bandwidth can be measured quite nicely in a number
of circumstances with ttcp or netperf. 

There's a need for keeping track of number of bytes moved around the large
scale mass storage systems at NASA- the per-network i/f cumulative numbers
coupled with the tape<>disk bytes can do good things in telling us who
the system is doing and what its doing.