That's strange. I have the same behaviour as described in kb but with a e1000 network card in my VM.
Without 8.6 VMtools or with older tools (8.3.7) I dont have slow network performance...
Here is a more detailed description of the VM:
Windows 2008 R2 SP1
AntiVirus disabled !
CPU : 1 socket w 2 Core
8GB RAM
SCSI : LSI Logic SAS
Network Adapter : e1000
VM Version 8
The VM is connected to a Distributed Virtual Switch.
I upgraded from ESX 4.1 to ESXi 5.0 (515841) recently and I dont think the problem was present before.
If you need more information feel free to ask...
Thanks for your help.