Sorry for the delay, but I just wanted to mention that the SCOM R2 sizing helper has had an update about 2 weeks ago. You can get the Operations Manager 2007 R2 sizing helper here.
I use these a lot as they help with getting basic sizing recommendations to build into your design documents. Also be sure to pick up the SCOM 2007 R2 design guide as stated below:
“The Operations Manager 2007 R2 Sizing Helper is an interactive document designed to assist you with planning & sizing deployments of Operations Manager 2007 R2. It helps you plan the correct amount of infrastructure needed for a new OpsMgr R2 deployment, removing the uncertainties in making IT hardware purchases and optimizes cost. A typical recommendation will include the recommended hardware specification for each server role, topology diagram and storage requirement. The Operations Manager Sizing Helper is most useful when used with the Operations Manager 2007 R2 Design Guide ( http://go.microsoft.com/fwlink/?LinkId=184377).”
Have fun designing and scaling your OpsMgr deployments!