Woops, you missed this post from late 2005 where mentioned that we are enabling BES which requires a windows box:
Wireless
The top 3 reasons I like the BES solution better than the rest
1. The end user experience of BlackBerry with BES is phenomenal
2. Security - banks & traders rely on this stuff
3. Complete Administration
First Runner Up: No device footprint (no per-device install)
Second Runner Up: OTA provisioning