Are Harbeths really "all that?"

They were principally designed with voice in mind - drama and radio for BBC. They have a great midrange and will help make a bad recording enjoyable. I don't think they are exciting or the last word on a full orchestra, big band or rocking out the neighbours with ACDC.

However, they are great at what they do!

Horses for courses - if you want to hear a funky big band or Mahler at 100 db SPL at the listening position with tight punch in the stomach percussion and clear tangible deep bass riffs then I would recommend something else! (But remember you can listen to Harbeth at more modest levels all day long and enjoy the polite and resolving sound)

Actually the wide cabinets are preferable to narrow cabinets for edge diffraction

Not really. Narrow cabinets less than about 5 to 10 inches wide can be very good (smallest is best and this is important in the mids and HF which is why you sometimes see a triangular mid and HF with a woofer box below). 1 to 3 feet is less good (generally manufacturers will place the tweeter off center which helps). A flush wall mount is the best of all as there is no diffraction and ALSO no rear (wall behind speakers) quarter wave cancellation in the bass (below about 400 to 600Hz) Recall that bass radiates omniderectionally whereas MF and HF rediate mostly forwards into a "half-space" - so in order to create the realistic illusion of a point source then you should really try to flushmount in a wall.

So are photography analogies -- over- and underexposed, lighting, soft focus, Kodak vs. Fuji color (hmmm...not sure I remember what those two look like these days).

Not sure of the photo analogies but the bokeh on my Nikon AF-S VR NIKKOR 300mm f/2.8G IF-ED is awesome and yet the subject is as tack sharp as you will ever find. I even have a Polar Bear shot on my virtual system for fun (a photo taken up North in Hudson Bay - yep - that Bear is wild and NOT in a Zoo and it was extremely COLD outside)

What would be the equivalent of bokeh in the audio world?

Dodgealum,

Watch out - IMHO AN fans are extremely protective and defensive of some of their classic retro type designs. You may have just entered a mine field - though I hope not as too many threads seem to take a bad turn these days.