My own controller and my friends controller have both encountered faults - mainly staying connected to the console, but also problems with buttons and the play & charge.
When we tried to register a return, the only option we have is for Self Postage... To the Czech Republic. Which costs £54 for tracked international mail.
We spoke to Xbox Support who basically said there was nothing they could do and yes we would have to pay the whole postage costs, when we could go buy a new controller for £44. I guess Microsoft know that the return postage exceeds the cost of new controller at stores so it makes them even more money.
It's absolutely disgusting that Microsoft deliver faulty product to early adopters of the Xbox One and treat them like dirt - not even covering postage costs for replacements.
So be warned - if you were good enough to pump money into Microsoft on their launch of the Xbox One.... you're probably going to end up with faulty goods which you have to pay huge amounts for international shipping, and they really couldn't care less.