Ran into a packet loss issue today. Normally I usually only use E1000's in production. We had some Server 2003 VM's running with Flexible NICs. Caused intermittent packet loss, once we changed them to VMXNet2 adapters, the connections were perfect.
http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1001805
