I'll start by saying that I expect Moose to be ubiquitous. If it's not now, it will be.

Moose has a huge loading time that makes it unsuitable for many tasks. On my (somewhat old) computer...

$ time perl -e 'package foo; use Moose'
real    0m1.052s
user    0m0.880s
sys    0m0.044s

$ time perl -e 'package foo'
real    0m0.008s
user    0m0.000s
sys    0m0.008s
[download]

I see no problem using Moose inside big long lived applications or frameworks like Catalyst and alike. But using it in a generic CPAN module unnecessarily limits where that module can be used.

BTW...

$ time perl -e 'package foo; use Params::Validate'
real    0m0.066s
user    0m0.028s
sys    0m0.008s
[download]