Talking about altitude excursions et al; doing the IMC rating really tightened my flying up. Mind you, it's easy to fly accurately when you are staring at the instruments. Having said that, if I never have to do an instrument approach in anger, the IMC was worth it because what I learned about accurate flying has crossed over into my VFR flying, I don't like being more than 50' either side of my chosen altitude or more than a couple of degrees off chosen heading. Not that it matters so much I suppose, it's just a question of having some pride in your flying.