A few weeks ago VMware acknowledged a bug in ESX that translates into poor performance when it runs Microsoft Terminal Services workload on Intel 5500 (codename Nehalem) CPUs with Hyper-Threading (HT) enabled.
The issue emerged in independent benchmarks published with the Project Virtual Reality Check (VRC) framework and Citrix has been quick in suggesting that this demonstrates the flaws of the VMware EULA.
The founders of Project VRC rerun the benchmark with the patch and the results are considerably better.