I'm worried that Dylan may be repeating one of the biggest mistakes of Lisp, namely that of supposing people would rather move to a new Dylan world than use Dylan in their existing worlds

I would also suggest that a successful language can make a fancy environment for it seem like an excellent thing, but not the other way around. Saying "use this language becuase it has a great environment" works less well.

The Dylan community needs more competent macro designers. A few people who know how--and more importantly, when--to extend the language will go a long way.
Unfortunately, Dylan makes you deal with two separate hard problems at once: good macro design, and macro implementation. The infix syntax makes the second part rather hard.

see also: What a competent macro designer msut know