Quite a lot, actually - but still with a bit of a caveat: I've been out tonight (concert - it's 1:30 (am) here now), so I haven't had time to rate and process today's images. I went out with the two Noktons to get a better idea of what the f/1.5 version can do. They're very different beasts - the f/1.5 has a decidedly warmer signature; until I've reviewed all the images, the jury's out on resolution and overall IQ, though. But the biggest difference is definitely bulk. I thoroughly enjoyed the handling of the f/1.5 today because it's more compact, and while the f/1.2 feels even more positive and better built, the f/1.5 leaves a very solid, balanced impression. I think I got exactly what I wanted: a very good lens that's decisively smaller and lighter than the one I already had (and it's also cheaper, so less of a worry to take everywhere).So Matt. You got yours. How are you liking it so far?