I have a nice big hill on the way home from work each day. Takes me about five minutes to get the entire way up. (I'll have to confirm that; I've actually never timed it.)
I'm running 48x19 on my steamroller (66.5 GI), and that seems to be plenty fine for flats (18mph more or less at 90rpm cadence) and it's a nice burn up the hill.
It gets pretty spinny going down that same hill on the way in, but I run front/rear brakes, so I can keep it in check.
So, anyway, not sure what I'd run if I had a whole mess of hills, so take it for what it's worth.