There’s two ways to apply strokes to shape layers in Photoshop CS6 — via layer styles, which have been around since version 6 (that’s the ancient version 6.0, not CS6), or via the all-new vector shape options. They may appear similar at first glance, but there’s some significant differences.
After some thought, I’ve decided that I agree with John Gruber and Dave Wiskus, but not for the same reasons. I don’t think Retina displays have much to do with it at all — in fact, Retina displays are even better at displaying subtle textures, lighting and shadows. Those extra pixels go a long way in providing additional suspension of disbelief for realistic user interfaces.