Thank you Kurt Varner for a great article, and while I agree with almost everything in it, there’re still some problems with the designing in “non-real-resolution” (yes, when you say “1x”, you’re actually designing in half the size of the real device resolution mostly).
The biggest issue with “1x” for me is that when you need a really thin, true 1px line — you have to use “0.5px”. And at the very moment you put “0.5px” in the measurement window – you feel that it’s just not right. And sometimes you really need those “thin 1px lines” that would work just fine on the real device. Also if you ever want to use icons that were designed for the regular resolution in your mobile app design — you’d feel that they are dat thicker than you want them to be. So every approach has it’s own pros and cons and as much as I appreciate the idea of 1x I can’t use it all the time.