The official tool for capacity and sizing guidance for Operations Manager 2007 is System Center Capacity Planner, which is due out in the second half of calendar 2007. It is available now as a beta here. To download the beta, you will need a Windows Live ID or Passport Account.
In the meantime, the product team has issued the OpsMgr 2007 Performance and Scale Guidance white paper. This paper covers a lot of ground in its 10 pages. The main topics are:
Attached is a copy!
Senior Technical Writer, Operations Manager Documentation Team
I wonder if I could fit more words into the title if I put a little effort into it ;) On the MOM Product
This Blog entry references the download location of the System Center Capacity Planner 2007 Beta from the Microsoft Web Site. SC CP 2007 provides detail Sizing and Performance metrics for System Architects designing Exchange 2007 and System Center Operations