How accurate is the ridewithgps on hill inclines? Can some of you test this against what you already know and give me any thoughts?
All mapping software uses some form of the USGS data set for elevation. These elevation points are fairly spread apart so fine-grain elevation measurement is typically a shot in the dark while average climb gradients are going to be more accurate. Ridewithgps uses a better algorithm than other SW but it has issues with crossing a bridge over a canyon. In those cases it tends to follow the ground contours. I know the owners/developers are working on a fix for this issue. You do not want to look at a specific point on the route and assume that the listed gradient is correct.
A GPS with altimeter is always going to be your most accurate option.