Let me start with a disclaimer, I am the author of Moose, so any opinions here might be a little biased ;)

Specifically, I was wondering how many OO modules are using Moose.

By searching for "Moose" on http://search.cpan.org, then looking at the META.yml and Makefile.PL files, I found the following:

• Class::Workflow
• Mail::Summary::Tools
• POE::Component::DirWatch::Object
• Date::Biorhythm
• Class::Component::Recipe
• Reaction (the CPAN version is a very early release of this, go to #reaction on irc.perl.org for more info)
• WWW::Facebook::API::REST::Client
• Verby

In addition to these modules, we have been using Moose quite a lot at $work. We use it both in the refactoring of older code (I spent a few days once just replacing hand-coded accessors with Moose attributes), and in producing new code. But as I said above, I wrote it (and $work sponsored that effort), so of course we are gonna use it.

I know of several other people who have used Moose successfully at $work as well (passing code reviews and deplying successfully to production). And there seems to be a fair amount of people in the POE and Catalyst communities who are playing around with Moose too.