Once you have been able to root your HTC phone you will be able to enjoy enterprise WIFI connectivity (such as 802.1X / WPA) and with it, you want to obviously connect to your Exchange server.
In my previous post I mentioned that rooting your HTC will result in loosing ActiveSync. But with TouchDown from NitroDesk you get an Exchange client being able to receive push notifications, which worked faster in my tests on the HTC vs. my Entourage and Outlook clients.
TouchDown provides full ActiveSync support, the ability to instantly and automatically synchronize changes made to the Exchange Personal address book into the Android phone book, and support for setting peak hours to specify when to automatically check for changes to Exchange data. A must have for any Android user.