I've started using Moose and like it quite a bit. I do agree with the other posts that say you should still learn how to do OO perl w/o Moose. But that tends to be difficult and there are many ways you can go about doing that. I think if you're starting a new project then Moose is the way to go.
I've also used Object::InsideOut, which is a lot like Moose and also helps protect your object variables from being tampered with.
Another note, I understand that Perl 6 objects will be much like Moose objects.. so learning Moose will prep you for Perl 6.
