This makes me think that the advice about 50/50 cofounders -- that you want somebody who complements you, not somebody like you -- is especially good.

If you're the tech guy and the other guy is the business guy, you have a conflict-resolution method in place for most things. You have final say on tech, he has final say on business. So you'd expect the difficult/troublesome decisions to be the ones where you've got equal say, like "do we sell for this amount of money?"