I am not aware of limitations caused by using FCoE
All VAAI Primitives are listed as being supported for 5.1
As for the VSI plugin that talks to the array at management level not across the FCoE so shouldn't matter what the connectivity type is.
I agree with Mike's post-- assuming we're talking about VNX to fabric or host to fabric hardware-FCoE (and not VMware's Software FCoE, which may its own limitations).
George, are you looking for a document on the EMC side, or on the VMware side?