> So I need to switch to exotic JVMs to get better performance?

Depends what you mean by "better". HotSpot is optimized for peak performance (which is higher than that of other Lisp runtimes), and to suit the needs of server-side development. Other VMs target other uses -- fast startup, embedded etc.

> If the JVM would be a better match, then Lisp implementations on it would have a better start-up time - like most Lisp runtimes have.

It's already a better match, because that's what most Lispers prefer. If you mean it could be even better than it is, then I agree. I also agree that it's not the best match for, say, Racket. Now, it's perfectly fine if you prefer Racket over Clojure, but most people prefer Clojure to Racket, partly because overall the runtime gives them more of what's most important to them. Would it be cool if the JVM had more features that would allow it to be a better match for Racket? Sure.

> Does the number matter

Yes, because Clojure is the most popular Lisp, the features it has are probably the ones most important to Lispers.

> Things like 'no TCO' in the JVM are no question of the number of people using it, it's simply a fact.

Yes, but how much not having TCO matters can be answered by popularity. That people use Clojure much more than they use Lisps on runtimes with TCO suggests that other things matter to them more.

> neither currently nor in the near future

Currently, no. Near future -- probably. I'm the technical lead for that project, and it's very likely that delimited continuations would arrive soon (in fact, you can already build the prototype today, and early access builds will be available in a couple of months).

> Now the usual arguments about TCO are ...

Well, as it's being addressed only now rather than, say, 10 years ago means that it's not a top priority, but judged to justify some reasonable effort at this point in time.

> TCO is not supported by the JVM, while this capability is a part of many other runtimes.

True, but the fact remains that the totality of capabilities of the JVM is considered more attractive by more people than that of most other runtimes.

> That's all great, but I don't develop huge backbones all the time.

I am not saying that you, personally, should definitely use the JVM, only that it seems that the JVM is a great platform for many languages, including Lisps, and that the use cases it targets are very desired.

> Your original claim was this ...

I believe I also said that I mean capabilities for the domain HotSpot targets. Obviously, other things may be more attractive for, say, embedded software.

> It currently provides no TCO at all.

There are other things it doesn't provide. But by comparing capabilities I did not mean one by one, but the totality of those of one runtime vs. those of the others.

> It's not about what I need, it's that capabilities like extending the IDE on the fly are still not available in an IDE like IntelliJ - why? After downloading a plugin, it wants to restart the IDE. Something which a typical Lisp system on a Lisp runtime brings for free, because of its capabilities.

No, that capability is definitely there. I'm guessing the IDE authors just didn't think it's worthwhile to use. NetBeans, for example, doesn't require a restart after downloading plugins (or, rather, rarely does).