Same issue, my sleep doesn't reliably, when I'm on battery and shut the lid, when I reopen the backlight usually doesn't come on. Can require 20 or 30 cycles of closing and opening lid before it comes on, or a reboot. Tried SMC, PRAM reset, all the other tricks listed in this thread, no help. Took into the Genius Bar, they took it in back and checked connections, no luck. I tried to return it a few days after I bought it, but was a "custom build" and purchased through company, could not exchange or get rid of it, and now I'm stuck. Apple wants a week to "fix" it but they don't even know what's wrong and given the problems on this thread it seems likely I'll just get another bad laptop and just be out one week and unable to use for work. Now I'm facing just writing off the Air as a loss and going back to a non-Apple laptop, which although not a nice OS at least works reliably. Adding my woes to this thread, it's not like anyone is going to be able to help me, but I'm hoping at least Apple will realize they have a problem here and provide a fix.