What is most interesting about the Conn phenominon is that only Conn seems to command this kind of intense loyalty. In addition to the general information about the horns themselves, I've seen whole series of photographs devoted to the history of the company and to the manufacturing processes, this for a company that has been defunct long time passing. Neither Yamaha nor Selmer (nor, for that matter, Kenny G) saxophones have commanded such loyalty to the extent that someone has gone to such trouble.
While some may intensely "not like" the Conn horns (and, with the ergonomics, the mouthpiece limitations, and the general funky smell that is part of most of them, there is substance there not to like), there is also the reverse side of the coin. Whether or not they are meant for all, it is clear that they are meant for some. The issues with the sound that some find with them (and are articulated here quite well) are clearly not a problem for others. (I have found that the classic Conn alto from the 1920's quite to my liking, but agree wholeheartedly from my limited experience that classic Conn baritones are to be avoided. Since tenors aren't my cup of tea, I don't even have to worry in that area.)
However, it's quite easy to ignore one of the biggest issues with all saxophones here: availability. Finding a restorable Conn horn (with the exception of the overly-popular tenors of certain vintage) is very easy. I got my alto for all of $25.00, filthy stinking mess though it was at the time. Convinced as I was of the Conn advantages (great sound being the foremost of them), I put about $700 into a full rebuild minus the gold plate, and I am more than pleased with the end result. Purchasing a viable (that is to say, "capable of restoration with minimal investment") Conn can run as little as $50 on eBay the last time that I ran a check. Getting any other "good" horn (Selmer or Yamaha) for such a price is unheard of.
Purchase and restore is not for all. But, many who like Selmer classics would jump at such a chance. The beauty of the Conn instrument is that the price is right. The days of finding a relatively undamaged Mark VI in a pawn shop are long gone; improved communications have all but eliminated the "knowledge gap" that used to enable such finds.
I would never praise the vintage Conn instruments for their ergonomics. I always claim that the good Colonel (a Colonel only by courtesy, mind you - along the lines of Colonel Saunders of Kentucky Fried Chicken fame) used an orangoutang as the model for his user's fingers and hands. They are also "old", something that comes with old cases, the smell and thumb hooks suited for a foundryworker's hands.
But the sound (with the right mouthpiece) is what impresses me. Deep, full bodied and "throaty", something that classic "French design" saxes just don't have. The difference (to me, at least) at least merits a trial. And, with Conn prices being rock bottom for project instruments, it's a difference that many can experience. Try that with a classic Mark VI some time.
(In fact, you can even take the phased restoration position with one of these horns. Purchase the wreck, have a minimal rebuilt done (pads and mechanical) and then - if you like it - you can go the extra expense for the cosmetic aspect. Since comparable quality Selmer project horns are few and far between, it's unlikely that you'd be able to do the same there. And, forget about finding lower quantity instruments like a Big B.)
Some of the objections raised to Conn instruments also merit some discussion. The low Eb "fork" fingering on older Conns has historically been corked closed on restored horns. I've tried it both ways (having played similarly equipped Leblanc bass clarinets over the years), but I agreed with my technician that it was better left deactivated. The articulated G# absence was never a problem on any Conn horns that I have tried (mostly from the 1920's), since all of them had it there and enabled. And, the lack of altissimo keywork was never an issue for me. (For those who have a pressing need for such things, Conn's have their own complement of altissimo fingerings that are "off the charts".)
Ultimately, the proof is in the playing. Opinions such as mine and others are just that - opinions. An actual trial (and more than five minutes on someone else's horn) on a Conn will give you a good look at the good (the sound), the bad (the smell), and the ugly (the keywork - oh, how I hate those left hand little finger keys). And, it's something that most can afford to experience and make up their own mind over with an extended trial - something that's not easily said for other "must have" horns.