The interactivity was only getting in the way for me. And if the file was in a vector format, such as pdf, I could navigate in all the same ways using Preview (or another pdf reader).
But the interactivity is really cool -- not only can you pan/zoom, you can click on any function, and it'll take you to the exact file(s) and line where the function is implemented.
I wouldn't want to do that in a PDF reader.
You can pan and zoom with the mouse, too. The controls at the top right made me think i can't do that, at first.