Guess I'll continue spamming threads with this IMO helpful bit of advice:
It's actually easier if you don't try to "aim" for the corners and instead just move in the general direction of the corner without thinking. The whole point of putting the hotspots in the corners is that you can overshoot them and still stay at the right place.
Similarly, when using the Metro style apps switcher (on the left edge) or the charms bar (on the right edge) with the mouse, instead of doing it in two discrete motions (move to top/bottom corner, then move down/up), try just swinging your mouse pointer around the corner in one fluid motion. With a bit of practice it becomes a lot faster and actually kinda fun and addictive (or maybe I'm a weirdo). I wish the animation for the charms bar appearing was a little faster though.