When I lost about 20 lbs two years ago, it was blatently OBVIOUS on hill climbs. I mean, the ease at which I got up those hills in comparison to when I was heavier (thereby leaving me fresher for the rest of the ride) was phenomenal. But I lost the 20 lbs while training for tri, so I was also improving in fitness.

I think that once you get your bike fitness back, you will be faster...particularly on hilly rides. Just don't expect to go out there and fly immediately out of the gate.