There are lots of problems with getting it right, but my way to do it, which works 100% for me. is you have the 1px transparent border, you place it at 0,0.
Then you need to be in low quality, and Stage.scaleMode("noScale");
Everything works fine when your in that mode, however, to use it in High Quality you must do what that other guy specified, but that is quite hard when trying to get tile engines set up etc.
Nevertheless, for games, you should be in low quality anyways, the speed increase is extremely noticeable
