@VK5ISO:
Thanks for your accurate and observant post.
Like you, I've owned two Begalis with mixed experiences. I currently have an HST III which I purchased unused from a ham in New England. As advertised, it arrived new-in-the-box. Fortunately I've not seen the QC problems you have. I have the HST wired in parallel with an N3ZN-SL so I can switch from one to the other. Performance is quite similar actually.
My other Begali was a Simplex Mono, which was unsatisfactory. The Mono was unable to accommodate close contact settings. It would add an opposite element at the end of character if the points were set too closely. Hence an "S" would become a "V" or an "M" a "G." Very frustrating. Begali sent a .3 mm feeler gauge with the Mono and they weren't kidding. .3 mm spacing was the absolute minimum the key could tolerate without misbehaving. To be fair, the Mono is one of Begali's least expensive keys. Although for the same money one could own (say) a Kent which, while not as visually striking, is at least known for its reliable performance. I actually gave the Mono a 4 star review here on eHam, but in retrospect it should have probably been a three.
The HST, not unlike the Mono, seems to prefer somewhat wider contact spacing too, but not objectionably so. I actually like it quite a lot. It has a clever, easy to use return force adjustment that may not be popular if you're one of the rare ops the prefers a stronger return force on one side to the other. One complaint I do have is the cord connection. Why in the world would Begali mount it on the top instead of the rear in an unobtrusive location? It's mandatory to use a right-angle plug to prevent the cord from looping up ridiculously. And the sideswiper switch seems, at least to me, to be a superfluous afterthought.
I've had three N3ZNs and found all three to have similar excellent performance, not unexpected as they all use the same keying mechanism. Only the base or color varies. I sold a Junior because I found the base too small for home station use, yet too large and heavy as a portable. I use my second on a backup station.
I tried one of Larry, N0SA's keys. It was a single lever and, like you, I was attracted to its simple good looks and functionality. With translucent red fingerpieces it was quite striking. Inexplicably I had to clean the contact points every time I wanted to use it or it would not make clean, reliable characters. Go figure.
I had poor experience with a single lever Scheunemann purchased on eBay from an estate. It was an early model, with no centering mechanism other than spring tension. An absolute nightmare. This key has been re-engineered and is likely vastly superior to the one I owned.
I find I agree with W6MK as I don't find the Begali to be the "standard" unless it's for proliferation of models and mechanisms. Gotta give Pietro credit for ambition and an active imagination. Unfortunately, far too many CW beginners buy Begalis, having been impressed with rave reviews and impressive photos, when they would better served with less expensive, more prosaic keys. One can always move up to a premium key as one gains experience. Too many tyros seem to believe that an expensive key will instantly make them a proficient CW op.
And yes, I owned a Vibroplex VibroKeyer, purchase in 1965 as a Novice, with which I made thousands of QSOs. In fact the is the one remaining piece of gear that I still own from that era. I would return to that if deprived of some other more recent (and ostensibly superior) keys.