Steve, thanks, good posting.
P.S. I would extend Tip #5 to events, EventManager and the event collector.
The second half of the top 10 is here:
Also, added a new series: Top 10 Best Practices Architecting Applications for VMware Cloud
Author of VMware VI and vSphere SDK (Prentice Hall)
Blog: DoubleCloud.ORG ( Top 10 Best Practices,[Object Model|http://www.doublecloud.org/2010/02/object-model-of-vmware-vsphere-api-a-big-picture-in-2-minutes/],[Common Mistakes|http://www.doublecloud.org/2010/01/31/common-mistakes-using-vmware-vi-and-vsphere-sdk/], Tiny REST API, Cloud Application Architecture)