From the current version (0.98) of the Moose::Manual::MooseX are the lines:
We have high hopes for the future of MooseX::Method::Signatures and MooseX
I think it's a matter of differing perspectives as much as anything -- rafl is one of the aforementioned "more insane members of the community" while Rolsky is more conservative. It's up to you to decide who you agree with, and really I think that the most important variable is your own code.
MooseX::Declare is good code. It won't randomly blow up your machine, it's not awful for performance, and it offers a lot of nifty stuff while reducing the amount of boilerplate that you have to write. But it might change in the future, making your code refuse to compile until it's updated; it might make your editor and other development tools confused when it sees syntax that it can't parse, it might piss off your collaborators by making them learn a new module to work with your code, or it might piss off your boss by making it so any future maintainer has to learn a new module to work with your code. Which of those things apply to you, and to what degree? You know better than I do, I hope.