Has or does anyone owned this lens? As much as I really like the 2.8 that just came out, I can't afford to spend $500 on lens right now. I wouldn't be buying this right away, I'm just trying to get some reviews on this particular lens, to see if it's worth checking out. I'd mainly be using this for landscape pictures, and night photography. So as to give a better sense of what I'd be using the lens for.