More types of track lines
Currently there are 3 types of line for a track: simple color, according to speed and according to altitude. I think that at least according to speed/altitude change would be great to have. So track will change color when altitude/speed is increasing or decreasing. This will give nice overview of terrain/speed change.
Another idea is according to altitude and speed change at the same time. Color can be used for altitude and line style (length of dashes) can be for speed change (or vice versa).