Great for quick prototyping. Easily share the HTML prototype and let the user play with the UI, to get the actual feel of the interface. In case the software crashes, it creates the backup of the file so that you can recovered the file. Easy animation templates. Can create shared library. Easy to create user flows.

Great for creating clickable prototypes. I can create a very dynamic prototype that looks and feels real relatively quickly. Very few other prototyping tools offer interaction patterns that are as dynamic and complex as Axure. I can create things that resemble things in code (if user clicks X, set global variable Y to true, then if user clicks Z, show A). It's very easy to have a shared library and puiublish your work to a sharable link.

I like how easy Axure is to use. I taught myself everything about Axure and how to use it as a wireframing tool. I also like how there are so many online forums where you can go to get any questions answered and to troubleshoot.