Are Harbeths really "all that?"

I would call it trying until you get it right. ;-)

I've had two unsatisfactory experiences owning Harbeths, yet they continue to appeal to me every time I hear them at shows or a dealer's. So I'm about to make a third try. (This would be the definition of insanity, right?)

Sounds like there is some significant difference between the dealer's listening environment and yours. Or there could be a case of component matching.

Before you repeat the exercise it would be worth finding out why they seem to sound more appealing to you at the dealer's place than they do in your home.

I have a pair of Spendors, a "cousin" of the Harbeths. Neither has the modern, trendy, rather bright sound but they are extremely engaging for extended listening if your primary interest is acoustic instruments and voice. Though I think mine sound just fine with rock, r&b and the like, I can see that some people would prefer more "punch."

Finally, when auditioning equipment out, we often tend to play those "special" recordings that we think will display the attributes we want to hear. Yet when we dive into our more ordinary recordings once we get home, we can find a piece of equipment that sounded great in the store with select recordings is not a good match for what we listen to most at home.

I think you need to also look at them in context to the professional environments that they serve.

There are two camps in England: ATC and Harbeth-like speakers.

ATC are very precise sounding speakers that enable recording engineers like myself to hear minute differences between individual tracks and takes. They are essential to mastering and found in studios like Sony.

Harbeth, Sterling, Tannoy and Spendor are all derivatives of the original KEF driver-based BBC monitors commissioned in the 1970s and were designed to enable long listening sessions while editing dramatic and live performances for stage, television and movie production purposes.

They are very different in sound. I liken ATCs and their ilk to be more like white wine--bright, festive, with a brace of acid. I liken Harbeth to red wine, warm and full bodied. Some days you want a precise sound and some days you want a smooth sound.

I think the Harbeth 40.1s are a wonderful organic sounding speaker and will play well in most consumer environments. I think that Spendor is doing incredible things with the new A6s and KEF with their 205s and 207s. All have the refined sound you expect from an English monitor.
I think ATC 150s are a true "reference" product for studio production.

"All have the refined sound you expect from an English monitor."

"Refined" is an accurate and useful description for many high end audio components, in particular speakers, that come out of Britain I have found.

I'd toss DNM Reson ICs into that category as well. I use them to inject a bit of restraint and refinement into my system when called for.

I prefer to tweak my system towards the more subtle and refined sound when called for rather than make it inherent via the speaks.

Of course, as has been pointed out on person's "refined" may be anothers "boring" and vice versa so YMMV on any particular day even just depending on your own personal mood.

I also like wine analogies very much when discussing the various fine points of audio!

Yes, wine analogies are very good. 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).