I've been curious about the Jupiter JAS1100 series for a few years. It's their top-of-the line pro model. When one finally showed up online at a great price with a good return policy, I bought it. Here's a mini review.
Indeed it is a pro quality saxophone. Intonation was very good indeed. The tone was also good… on the dark side. Ergonomics are very good… natural and comfortable. Almost as good as Yamaha. Unlike most Taiwanese or made in China saxes, it is a lightweight horn. The mechanics are also very good with more adjustment screws and features than many other saxes (even "pro" models).
The adjustable palm keys are very handy and do not get loose from playing. They are inspired by the adjustable palms that Keilwerth and B&S implemented but these seem to be an improved design.
The feel I got when playing it reminded me of the vintage 1950s Couesnon altos. Meaning; good sound, good intonation, compact volume (i.e. classical). If you blow hard you will not get the type of projection that you would get with the Yamaha or Selmer altos for example. I did not measure the bore, but it plays like a smaller bore horn.
So, did I keep it? No because it doesn't do anything my current horns can't do. It also seems a bit timid in the projection department as mentioned above. I think it would be an excellent second-hand alto for a classical player who can't afford a Yamaha 875EX or anyone looking to step up.
(I'll be posting some more information about Jupiter soon.)