I love Silver Efex Pro II. It does great B&W conversions, but you can also use it for improving color shots if you have Photoshop. The idea comes from Dan Margulis, though he didn't use NIK. Basically, I do all my cropping, color correction, noise reduction and global exposure correction in LR. Then I drop it into PS and create a second, duplicate layer, which I convert to B&W with Silver FX. I do all my contrast, structure and sharpening adjustments on that layer, then change its blending mode to luminosity. It sounds complicated, but using macros and scripts it's really quite fast. One side benefit is that I end up with color and B&W versions of every shot--sometimes it's not clear in advance which is going to turn out better.