I have been playing around a lot with the Custom Map section and I find the use of white and yellow as indicators for start/end min/max to be problematic. Given that the majority of your users are male and males tend to have more color blind/color weak issues, it would be nice if you had someone take alook over the use of colors in the UI.
For example, I often press the Min/Max button multiple times because the difference betwen a white dot and a bright pastel yellow dot is very hard to pick up. My suggestion is to either use a more contrasting color like red or blue against the white or if you have to use yellow for consistency/programming reasons, make it a less bright, more saturated yellow to provide a higher contrast to the white. In addition, I find the visual change in the graphic for min/max to be very subtle and not much help in determining which end of the range I’m working on.
In geenral I find the UI fast to get around on, but there are areas like the above that really slow me down due to the color/style choices made.