The advantage I see to use a switch as DHCP private messenger, is that you have a point less than defect in your network.
A server would have to have a network cable and a door attached to it and a whole configuration on the network for it to reach the target machines. Such as the DHCP relay switches or routing between Vlans.
To put DHCP switches in the Vlans not need to be routed to see.
I have never used an extreme switch as a DHCP server but have used other network devices in that capacity. I usually did it as a one off solution where there was no other better suited infrastructure available to handle DHCP. A (very) small remote office for example. I prefer to use a more robust and manageable solution like a windows or IPAM.