This is a follow-up to post that I last made on whether customers should upgrade to vSphere.  One of the big things in vSphere is the new Enterprise Plus SKU, which is a cost upgrade for all existing ESX customers.  This news posting details the issues surrounding the pricing to upgrade to vSphere.  It's not a surprise given the current economic times. 

http://searchservervirtualization.techtarget.com/news/article/0,289142,sid94_gci1359167,00.html