Is there any downside at all to enabling portfast on an ESX server? Do I have to worry about vSwitch creating loops or any other reason that would cause a loop doing this? It is a end host after all.
i dont think so. as far i as know you need to enable portfast on the interface to prevent any connectivity issue. you dont want your ESX server taking part in spanning-tree transtion process so with portfast the port the ESX server is connecting to will transtion to forwarding state.