Few things are more consistently frustrating than trying to grab the edge of a window that's stretched out to the edge of one monitor in a multi-monitor setup, but adjacent to another area. With a single display, you don't carefully navigate the mouse to the exact location... you whip it all the way
to the right (or top, or bottom, or whatever), then nudge it back a tiny bit. It's a reflex.
With two or more monitors, that scheme falls apart. Try it sometime... it's a LOT harder to grab things along the right edge of the left monitor in a dual-head setup, or vice-versa.
What I'd propose is making the zone between two adjacent display areas conditionally "sticky". If the OS notices deceleration as the mouse pointer approaches the transition zone, it would make it "stick" to the edge of the display unless the user keeps moving the mouse and some motion threshold (say, 20-30 pixels) is exceeded. On the other hand, if it notices ACCELERATION as the pointer approaches the transition zone, it would semlessly cross over to the next display without hesitation.