Will microwaving lemons make them easier or more efficient to juice?
It makes the lemon easier to squeeze. I think it has the most effect on the peel; it's softer and more flexible when warm, so you're able to get more juice out of it than you could otherwise if you're juicing by hand. That's especially true if you're trying to juice several lemons - you'll just get tired and stop being as thorough if it's harder.

It definitely still makes it easiser if you have the squeezer-style juicer, since those do basically turn the fruit inside out in the process. It probably doesn't help as much with the kind that you push the fruit down onto.