The current charts (pie,bar) aren't quite applicable to get an overview about the visitors screen resolutions.
The obvsious reason is that pie and bar charts are made for simple, one-dimensional data sets but the number of visits per screen resolution is a perfect two-dimensional data set. In fact, the screen resolution values consists of two parts: the screen width and the screen height.
One of the best and simplest visualization type to display two-dimensional data sets is the scatter plot. You can see the difference in no time by looking at the attached prototype. In my opinion, this is the only way to make the screen resolution stats usable.
I got the scatter plot running with OFC, but there are several improvements needed:
probably too much work for only one report.
There's a bug(?) in OFC where set_range($min, $max) will undo a previous set_step($step) -- the workaround is to call set_range($min, $max, $step), or call set_step() after set_range().
I'd like to see this in core. Should be easier after we merge Gall's Scatter Visualization code into core and libs.