FCoE is not "just Ethernet"
*Full disclosure - I'm a CCIE and that does not necessarily mean Cisco to the death by any stretch.
FCoE, pushed by Cisco to the largest degree, requires storage licences for all the (Nexus) switches in use, a dedicated storage VDC if using 7ks (which can't be used for anything else) and appropriate QoS policies in place. This all facilitates "lossless Ethernet" which is different to "just Ethernet". If it were "just Ethernet" you could run whatever the hell you liked over it, like you can with iSCSI and just have your QoS in order. FCoE only has the layer 2 in common with boring old Ethernet and as such is much more of a PITA than iSCSI.