Ted,
I think a lot of your work has potential for b/w. My main crit would be that you're being too conservative in preserving tones... sometimes drama is more effective than accuracy IMO.
BTW, the second shot was done with the 12mm, not the 21 - the buildings are the same size as in the last two 😉
I agree with your comment that it would be nice to find a sharper 12mm - it's not bad, but it's not great. To my eye (I don't have one to compare) the 15mm looks a bit sharper, especially the samples I've seen on the M8, but the vignetting makes it less attractive on the R-D1. It does at least have the advantage of being fairly consistent across the frame, so you can use some post-prod sharpening without the center looking overdone.