The JU-06 does seem to be in demand though. I am seeing the used prices going up all the time. Now, I am seeing them go for as much as $700 - $800! Somebody is driving up the price. I have one of each of all the Boutique series, and two of the JP-08 because that is the one that I feel benefits from chain mode most. That is a total of 12 modules. Several, I got as "used" (repackaged by Roland that had apparently been demos), at very good prices. For more modern sounds, I have the Roland Integra-7. For a sequencer, I have both the old Roland MSQ-100 (a period piece from when these original synths were new) and the Yamaha QY-700. For a midi controller, I have the Roland A-500Pro.
It remains to be seen as to what else Roland decides to remove from the Boutique line, and what they intend to add as new product this year (if anything). I believe the JX-03 and A-01 have been discontinued, but the others apparently are still in production.
To me, each of these modules has its own flavor and is therefore worth owning, but others may certainly feel otherwise. One person I know suggested it was not a good idea to get the Boutique modules, when you could get a Roland Jupiter-80 with 256 voices.
For me, I would prefer separate modules small enough to fit in my condo, each with its own appropriate interface of knobs, buttons, and switches, and each doing one thing well. If I had a System 8, for example, I could load a "personality" such as the SH-01a on it and then the whole keyboard becomes that, but the interface of the keyboard doesn't change, so it is not optimized for the synth personality it is currently playing. With the Boutique modules and the KVGear stands, I have a bunch of flavors, each with its own appropriate interface, all in a very small space. I can see value in something such as the System 8, so I am not saying it has no value. I am saying that my own musical vision is quite different.
I really still enjoy listening to music created in the late 70s/early 80s during which the synths were quite limited by today's standards. Those artists (Suzanne Ciani and others) used the synths, with all their limitations, in very creative ways and created some wonderful music. The Boutique series recreates that environment quite well.
From this perspective, having BOTH the SH-01a and JU-06 (though not the JU-06 at today's selling prices!!) makes sense to me personally. I found a course on programming analog synths at Udemy that uses the SH-101 to teach on. Having the SH-01a was perfect to work with that course. What I learned is then applicable to the other analog recreations in the Boutique line (except the D-05).
Tony