I post this because I have always had this gut feeling of "don't install BES on SBS" but everyone around me says it works. I have installed it myself and it works, but I hate it.

Source: Mickyj.com

You will hear it time and time again. Don't install Blackberry Enterprise Services (BES) or personal, on your SBS box or member workstation of the domain. BES seems to interfere with OWA, OMA, IIS and Certificates (Especially Self SSL). I have numerous clients who have installed it to SBS 2003 and their event logs are a sea of red. It breaks numerous items and strangely, it is never the same things that break for each client. It would seem uninstalling BES does not fix the issues. The personal workstation software can't roam if you use roaming profiles, meaning you corrupt users roaming profiles, cause popup errors and the clients can loose files. The way around this is to bypass the Blackberry folders in the local profile using group policy. Everything else roams except these folders. Blackberry have special permissions and monitoring on these folders.

User settings Configuration/Administrative/system User profile/Policy
Exclude directories in Roaming profile
Application Data/Blackberry Desktop

Now there is a new beast on the block. Blackberry professional. I have no personal experience with it however a quick look into the Microsoft newsgroups shows users are having issues and recommending against using it. The Blackberry site tells us it is designed to work with SBS. Looks like email forwarding, cloud Blackberry services and POP3 are still the best solutions. (Or get Windows Mobile or an iPhone)