Noticing a considerable lage in the curve editor’s marquee selection, when clicking and dragging a box around keys, the selection doesn’t record as soon as the click occurs. So, often the upper-left key is not selected (if you click and drag from left to right, top to bottom).
Noticing also that the proximity to keys not meant to be selected is a little fuzzy - it can be very easy to select keys that are not meant to be selected if they are close to the selection marquee.
Just ranting here, but maybe there is a way to optimize the performance/granularity?