I think this has been known for a while
Last summer I started having problems with my sleep/wake button taking several presses to work sometimes. It would be fine for a while, then take multiple presses for a few days, then go back to working again. I googled and found that others had the issue and Apple replaced their phone, so I figured I should do it before my warranty ran out. Haven't had the problem once with the replacement.
I guess this means they're going to replace even those phones that are out of warranty (one year in the US, I think the EU mandates a longer warranty over there) Sounds like good customer service to me...