Well, I don't claim to be the world's expert in these matters. But, I do have a touch of experience acquired here and there.
(My very first bass was a Buffet in A, inherited from my paternal grandfather. An Albert system horn, it proved to be a problem for teachers everywhere, and my parents unwisely traded it for a "real" (read, "Boehm") clarinet before I hit high school. Incidentally, it only ranged to low E.)
I have bought quite a few Selmer (Paris) horns (say twenty in good round numbers), of the clarinet, bass clarinet, and saxophonic varieties, over the past forty years, most of them new stock purchased from a selection of like instruments. In that grouping (including all of the horns that I tried before purchasing that one "special" instrument), I encountered precisely one manufacturing defect out of the box, and that pertained to the stitching on a Traypack case.
Intonation problems here and there, of course - no instrument is completely immune to those issues. But, as for fabrication, quality of materials, and fit and finish, no - back in my buying days.
However...
Recently, I made an appointment to view the latest line of Selmer bass clarinets. I've had my primary bass since 1971 or so, and I worry about it cracking.) The horn that I tried was a demonstrator, and the materials and fit and finish on it were just fine.
The design, however, was lacking. Too heavy (as a result of a huge number of rod keys, rather than the classic trill and lower joint key designs), and a couple of weird key linkages for the left hand little finger that were just not working, for whatever reason. It's the first Selmer instrument that I gave the "do not buy" sticker to in all of my years of association with the brand.
But, perhaps my overall experience was atypical.
And student horns, on the other hand...well, quality issues there are best left undiscussed unless you are presented with one.
As for music, jazz is what it is. Some love it, others detest it. Most of the jazz crowd that I run with are fond of using the "extreme" notes on their horns, both high and low. If any of them were into the bass clarinet, I'm sure I'd be hearing low Ebs every little whipstitch. Thankfully, they are either too poor or too cheap to buy one, so they stick to the sax (invariably the poor, oft abused tenor).
(I don't ever loan out my treasured extended range bass, this for fear that they might get some ideas about working around low C...)
As for classical and other forms, I've played everything from Mozart to Lukas Foss. With the salient exception of Wagner, whose works in their original forms are not all that common outside of high concert halls, I have had occasion to use the low Eb in perhaps twenty to thirty compositions, almost always when the original work called for a bass clarinet in A. The low Eb is there for just that very purpose, and most casual, non-Wagnerian operatic bass clarinet players are going to die and go to their well deserved place in heaven without ever needing the low Eb.
With modern music, it's bound to be a bit more common. However, the casual player is just as unlikely to encounter much of this, since most non-professional orchestras shy away from performing "new" works.
Even ol' Lukas didn't want me down there in one of his improvisational works that he conducted back in the 1970's - he told me so himself when I asked him for his parameters (since the chart gave very little guidance to begin with). I kind of cheated and snuck a little into the cadenza at the end, where everyone and sundry was (in effect) performing the same florid melody line (playing the same written pitches) but each in the key of their particular instruments.
So, jazz and "modern" art music, yes. And, Wagner and a couple of the Russian and Slavic composers as well. And, God help you if you don't have it in concert band music - I seem to remember playing low Eb in every other piece that we performed that wasn't a transcription of Rossini or Beethoven.
In fact, I'd be far more worried if the bass in question didn't range up to high F or F# without speaking or pitch problems. For some reason, I've been seeing a lot more written notes well above the staff these past few years, both in modern "art" music (I still do some classical subbing) and in Broadway shows. I'm probably moving in the wrong circles these days...
One area where my low Eb key gets considerable work is when transposing baritone charts "on the fly" in pop music. When all of the other saxes are on flute or clarinet and the baritone chart is marked "blend" or piano, it's a sign that the arranger thought that a bass clarinet would be hard to come by in a typical group instrumentation. I just grab my bass, use the classic "Eb horn to Bb pitched clarinet" transposition trick, and go to town. I imagine that most don't bother with this, though. In fact, on used charts where a bass clarinet is called for, I almost always find that some previous baritone player has gone ahead and penned (it's never in pencil) in the pitches for the baritone, thus making them both hard to read. Bozos...
