I'm currently enrolled in Theory and Composition at the University of Alberta. Last term my composition instructor suggested that I take a look at NoteAbility for my notation.
I'm doing contemporary music, so I find that finale is extremely limited for what I want to express. I hate how it's always trying to help me!
NoteAbility allows you to ties across systems, change you stave to 2 lines (or any combination), place notes where ever you want regardless of the time signature, and dozens of other features with a single click. It is also 100% compatible with illustrator: meaning that you can draw an image in illustrator and click and drag it into your composition. As well, NoteAbillity is entirely composed of vectored images, so when you're done you can move the whole piece into illustrator and manipulate every line and note head. I mean everything!
It is not suitable for beginner notation (it lacks any idiot-proofing), but provides a completely flexible solution for advanced notation. Unfortunately it is only for Mac.