We are big fans of the monitoring tool Cacti and use it extensively throughout our network. Although the reporting function of WCS has gotten better, we needed to be able to see the client counts per wlan for a longer period (up to 1 year).
Using Cacti http://www.cacti.net/index.php
I was able to add in the templates for the 4400 controllers http://forums.cacti.net/viewtopic.php?t=12863&highlight=4400
and the aggregate plugin http://forums.cacti.net/viewtopic.php?t=19474&highlight=aggregate to summarize the associated station count per wlan per controller and then summarize them all on 1 graph. see attached.