I am new to all this. I haven't used lightroom yet, though I will in the next days. But I have been using extensively C NX2 (which came with my camera) and RT.
While I was experiencing once in a while problems with RT (images saved as black or nearly black), I like it a lot. I just installed the latest version (64 bit windows), by the way, and haven't seen the problem yet since doing this.
RT gives me a lot of freedom in processing, and has a superior sharpening method (deconvolution). I can't get the similar results with NX2's high pass. The highlight reconstruction is also very satisfying for me.
Disadvantage: it is slow, and I can't work on parts of the image. (But there is always photoshop, and I am think delaboratory as an intemediate step might also be very useful.