Has anybody used this lens? I'm beginning to regret buying this 15mm Ultra Wide Heliar now. I reckon I'm not going to come across many situations in which I'll want to use it. It'd be nice to have some of your thoughts seeing as I haven't used either yet. My screw to m adaptor will be here tomorrow so I can try it out. I'm starting to think it'd be nicer to have a rangefinder coupled ultra-wide which takes the same filters as my 35mm and 50mm summicrons. Oops.