BuddyPress.org

You have a pretty large site Bill, so I would imagine that with as many blogs as you are running you could be spiking memory quite often. I would imagine that running wp-super-cache on the main blog (if not all blogs) would be extremely helpful to you even if you have the cache times really low. Any new posts on wires, groups, etc clear cache anyways, so content is always fresh.

Trent