I'll take your earlier self-promotion and buy your book if it covers administering Exchange on a
two-node active/active cluster. Does it by chance offer this information?
One thing to note immediately is that in an A/A configuration, Microsoft strongly recommends no more than 1900 concurrent users per node. And this is with SP2 for Exchange 2000. SP1's recommendation was 1500. Also, note that Active/Passive is Microsoft's recommendation, which of course does not have any concurrent user limits above and beyond the hardware specs.
This was first published in July 2002