I would love it if window snapping allowed me to do the "drag to side of screen to take up half the screen" but, in between my two monitors. Ideally this would be done by using a modifier key, so that you don't just always do this.
Example:
I have 2 monitors, left monitor, right monitor.
I want to put word doc1 and word doc 2 half and half on the left monitor.
I drag word doc1 all the way to the left, and windows detects the snapping bit.
I then drag word doc2 to the right side of the left monitor, while holding my modifier key.
word doc2 is now taking up the other half of the left monitor.

Not sure if this is possible to do or not, but I think this would be a REALLY great feature to have!