My first few years (Yes, YEARS) I spent much of the time with sore quads/hamstrings/calves after a hard workout. If I took it easy it wasn't bad, but after a hard (2+ hour) ride, I would almost always be walking funny the next couple days. Now, I spent the first couple years on a mtn bike, which is know for low-cadence "sprint" intervals when you are constantly climbing 10%+ grades of dirt. But even when I got into road biking, my muscles would still hurt after a spirited ride. I just took this to mean I was tearing down and rebuilding muscle. Now, after five years after seriously getting into cycling I can do an easy century without too much soreness the day or two afterwards. A long, hilly, killer ride, or back to back intense rides still put a little sting in the legs. It's just your body's way of saying you did too much.