I put some alpha-to-coverage example images up on the wiki this morning.
I'm hoping to get some more transparency examples, like to show what sorting errors look like, what it looks like when you use alpha test combined with alpha blend (like take a close look at WOW's grass), what screenspace stipple looks like, etc.
Images are always better than werds!
Anyone know of any apps that let you switch between multiple alpha methods, on the same content? I'll keep looking around...