We use Axure for both wireframing and prototyping. The reason being that if you use it to wireframe, you can take those wireframes and add functionality as you iterate- adding interactions, fidelity, and anything else, as needed. No need to re-create anything. I also love the ability for multiple designers to work on the same project at the same time, and the sharing service where you can provide links to your boss and other stakeholders.
It’s not perfect. It irks me that you can’t really design responsively, and sometimes the community-project feature is a bit buggy (We always save a local backup, just in case). Also they just went to a subscription model for the newest version. We’re working with 7, so perhaps they improved things in the newest version.
I am dubious of the new subscription model for Axure. On the surface it makes sense, but maybe not in context. It used to be you could get the basic program for a flat $120. Now they’ve split it into several different pricing schemes. The cheapest, for an individual, is $28 a month. Perhaps not a lot in the grand scheme of things, but I have to wonder if people will pay that monthly fee when they could get Adobe’s upcoming UX software lumped in with their Creative Cloud subscription.