If you read the Bru's Views, John Wible states that in his case the haze is protein haze from adjuncts such as flaked oats and wheat, not yeast.
I thought Heady Topper was pretty tasty. I didn't realize it was cloudy, but I was drinking it out of a can at a Phish show. I haven't had the chance to try beers from any of these other breweries yet.