We've been using nginx at engine yard for 4 years now and I can say that it is the most solid peice of software out of the hundreds of open source componenets we run. We have close to 15k nginx dEmons running if not more last I counted and it accounts for 0.001% of production issues/problems.
Can't say enough good things about this peice of software. It just works and it's smoking fast and very resource friendly. Thumbs up all around