My audio just went, after my MacBook Air's visit to the shop. Last time round they forgot to connect the battery, I was hoping they hadn't seated the audio board properly but no, they tested at the Genius Bar and said the board had gone.
At this point, I went in a proper strop, criticising the design and reliability of the machine with just a couple of rude words, mentioning how the logic board, the hinges, the hard drive (and coincidentally the Time Capsule that backed it up) had all failed in the last year. Then I apologised for my language, told him i knew it wasn't his fault etc etc.
Cut a long story short... I'm getting full credit for a replacement. Good on them. I was miffed a few months ago when I had to pay towards the hinge repair (I was on a deadline, couldn't manage a delay of even a couple days back and forth) but this more than makes up for it. It seems they're either accepting there is a generic problem with the audio, or else accepting the (convincing) evidence that my machine is a lemon.
But I think I have to put the money towards a MacBook Pro. Much as I love the MAcBook Air concept, I think the execution is flawed.