This particular topic comes up from time to time in discussions. Yes it is OK to run Exchange on VMware, and Exchange 2007 on VMware is a supported configuration… for more info, follow the links below:
The Podcast – Wednesday, Jan 14, for another round of the VMware Communities Roundtable podcast
The Webinar – Jan 15: Exchange 2007 on VMware: Technical Case Study.
The White Paper – Deploying Exchange Server 2007 on VMware Infrastructure: A VMware Internal Case Study