My customer has 2 N5ks and 4 2148s. The N5ks have VPC between them, and the 2148s are single-homed, 2 to each N5K. Am I corect in saying that an ESX box with a 4GB host etherchannel would have one connection to each 2148, and that the ports would be configured in a chennel-group on each N5K, and in a VPC instance between the 5Ks?
Well, in this case, I would preferably suggest you to even use the Nexus 1000v if you want to scale with all the vm's.
Otherwise the vswitch is fine too.
Under vswitch, bundle the 2 uplinks together (port-channel).
And physically have one to each FEX, that is how VPC will work.