The bulkhead seats tend to get used as a gangway (more of a risk than a baby in the bassinet in my experience), and the exit rows I think have fixed armrests which get a bit uncomfortable. I tuck myself usually into one of the sets of two at the back of the cabin, or on the right side of the centre aisle a row or two back. There's nothing absolutely ideal in economy but the leg room is generally ok, there's always the chance of someone going into full recline but that's the luck of the draw really and in fact you don't lose all that much space if you're reclining a little too and are sleeping.