I think Katee's Starbuck was a horrible person and ultimately a liability to the human race, but immensely watchable thanks to the actress and the scripting. The only issue I have with Sackhoff's portrayal was that she didn't seem to be able to pull off the f-word.
She may have seemed like a liability, except for that little fact that she lead them to Earth and everything. Not to mention fending off Cylon raiders like a boss in earlier seasons.
Anyway, that's just my reading of it. I think it depends on how much you're prepared to take with the proverbial pinch of salt.
Going back on-topic, I imagine that the big-screen Starbuck will emphasise the loveable rogue / magnificent b****** aspects of the character while not going too near the kind of darkness that we see from about New Caprica onwards.