Take into account 'accuracy' where such a value exists. Points/circles could for example expand to encompass a larger value corresponding to the accuracy value, assuming it's a numeric value. Which is assuming a lot.
Add ability to toggle whether to display altitude/depth data? If this is default off it would make the alt/depth scale less prone to being mistaken for a map scale indication since it would pop up when it's turned on.
Add easier and more obvious way of selecting different sample groups to display on the map. This is already available under 'Display options', but I would like for it to be more obvious and easier to access somehow.