In case anyone else is interested, I began to wonder what the impending announcement of servers based on Intel's next generation Nehalem processors might do to mixed ESX clusters. Since you can't mix AMD and Intel processors in a cluster, I was concerned that the NUMA architecture described for the upcoming Nehalem might have the same challenges when mixing with older, non-NUMA XEON processors.

Here is a link to the coversation on the Intel Server Room that includes a response I received from an Intel specialist:

http://communities.intel.com/thread/3099

Now the question needs to be answered by the VMware folks to corroborate. The next big question in my mind will be what affect, if any, will the next generation of ESX server have on this. I assume it won't make any difference but I will be looking to confirm this.