Pretty neat! Along with the better location accuracy / being able to modify them that people are suggesting it would be nice to improve the combination circles so that they're over their respective areas. For instance if I zoom in at just the right distance over Washington D.C. it'll show a circle above the city with a number in it and you can clearly see Baltimore as well but Baltimore has no circles until you zoom one more level at which point it then separates the circles.
The fist issues sums as the clustering algorithm, which currently is not prefect. Current clustering works on a grid. So it's possible to have two close dots not being clustered, because are leaving in the different cells of the map grid. Although I have alternative one which will try soon.
Example: http://imgur.com/a/A3Xtq
Also being able to double click on the map to zoom would be nice!