Crow Master has quite distinct feel to it. One player in our campaign used a Crow Master, though I have to admit that it was the bird that kind of took the spotlight there. I liked using Bard, mostly because I had this gorgeous model for it. That +1 to Will rolls did not come into play that often, so I'm not sure if Bard would feel like it's playing that differently.
Assassin from the new book looks like it might feel functionally a little different from the rest.