We currently have 35 users and started using BES this spring. We reactivate a unit maybe every week or 2, which seems kind of high-maintenance to me.
It's also had a seriously detrimental effect on reliability of the formerly stable server I installed it on. We have to restart the server 2 or 3 times a week. Bumping the BES services helps, but only a reboot restores normal operation. And then, not for long. If I had it to do over...and I may if I don't find a way to make BES play nice...I'd put it on either a virtual server or a dedicated box. All in all, I'm not real impressed with BES stability at this point.