by the way, id personally go for activesync type setup. (activesync is a native microsoft protocol)
it's standard in exchange 2003 and standard on Windows Mobile devices (ie PDAs)
as long as your handheld can talk to your exchange server, it'll do everything the BES does, and more, and at a fraction of the cost.
i personally use a nokia 9300 with RoadSync (activesync client for S80) and apart from the 80quid licence for roadsync (which you wouldnt need ona native WM device) it's completely free.
i only pay for data costs which in my case is ZERO as im on an uhlimited data contract (which is the same on our BB contract tho)
having tried both the blackberry stuff, and the native activesync stuff, i FAR prefer activesync.
its cheaper, less to go wrong, and it doesnt rely on any 3rd parties