Power users have been running server editions of windows for a while to over come various limitations of Windows desktop editions. But in my experience they were usually 'abusing' msdn or technet subscriptions to get the licenses.
I don't see any reason why you couldn't run a server, except that the licensing situation is still obnoxious.
Server essentials is kind of of a messed up product, like SBS was and I hate both. (I mean, if you sold 2 lathes for example with systems running SBS the customer would have a big mess since only one computer in the domain can run SBS...)
So that bumps you to server standard, which as you said works brilliantly, but at $1200 it just doesn't make a lot of financial sense to put that all over the place.
I guess on a $200,000 to $1.5M piece of kit, it's a footnote in the price tally... but still... its a ripoff; and probaby cheaper to stand up an azure domain controller, and run windows enterprise on the units; at least assuming you need more than one computer in the environment.