djb, Road bike with bottles and repair stuff is ~24 lbs., touring bike with the same is ~31 lbs. I can tell the difference between the two when climbing an overpass near my home. It isn't so great as one may think, but if I keep the T bike to the same gear inches the climb is a little harder at the same speed.
Same overpass with ~ 15 lbs. additional on the T bike and it's a drop a couple of gears time. Not so much because of the weight, but I like to stand uphill and usually rock the bike and the rate at which I can rock it is less with weight in the panniers, so now I'm climbing with more weight and out of my preferred rhythm, if that makes any sense.
Brad