There are a number of Parrot languages at various stages of development. As soon as they mature a bit, you might find people taking them pretty seriously. :)

That would be great. But I'm wondering why the authors of other major dynamic languages haven't chosen to collaborate and use Parrot as their primary VM.

Parrot 1.0.0 was released in March of this year. Give it time.

A new technology needs to be MUCH better than any technology it hopes to supplant. Of course "better" can have many different meanings.

Is Parrot 1.0.0 radically better than other (non-perl) VMs?

Mostly, because they already have a VM that works.

I guess, but many of them seem to want a more advanced VM. (http://news.ycombinator.com/item?id=656594)