Run, don't walk but run away from clustered exchange servers. The clustered exchange server environment I administered never failed over without an error. Setting it up was a nightmare and my predecessor got fired because he couldn't make it run. Veritas never ran correctly on the cluster. Finding support technicians that understood a clustered environment was difficult at best. After removing the cluster my system is working flawlessly.
The article writer mentioned the additional training and additional hardware costs but he forgot to mention the additional software costs. You must have multiple copies of Win 2003, multiple copies of Exchange Enterprise edition (standard won't work), multiple copies of antivirus software and multiple copies of backup software. (Veritas asked me if I had two copies of the software every time I called them.)
My clustered file server worked well but I never trusted and DFS works better in a distributed environment. I Finally shut off all of my clusters last month and haven't look back since.
Microsoft