Some folks around here who have made the switch to mediums-only have told
me they like the resulting arrangement much better.
 
In fact, a local commercial operator has remarked that outfitting the brood
(or extracting) frames is much easier, as he no longer has to use
cross-wires.  He orders crimp-wired foundation without hooks, and just pops
this into the grooved top&bottom bar frames.  That's it.  Since the
foundation is fairly shallow, it tends to sit centered in the frame well by
itself, without bowing.  Sure beats wiring or expensive plastic foundation.
 
The only things I'd be concerned about with mediums, other than the initial
greater expense per-hive, is the greater division of the broodnest (more
wood = barrier to queen?) and inter-connecting burr comb between the
stories.
 
A few decades ago Dr. C. L. Farrar favored a mediums-only system, using 3-5
boxes for the brood nest, and evidently had great success with this.  In
fact, he eventually incorporated it into his reknowned 2-queen systems. His
hive bodies were made to hold 12-13 of the medium-depth combs, which comes
close in total volume to a 10-frame deep.
 
Could anyone comment on the burr-combing problem?  Even with full-depth
multiple brood-chambers, it seems the bees prefer to "connect up" the combs
in the space between the stories.  Not sure if this is a natural
predisposition or more the result of an improper bee-space...
 
Cheers,
 
Joel Govostes
Freeville, NY