Discussions like these should really begin with a setting-out of the attributes most valued in a backhand, and which forms matter most. It seems just about everyone's talking about the backhand as an attacking shot, but what about as a solid, consistent (or error-inducing) rally ball? Or a passing shot? Or a lob? Or even a slice? And what about placement, pace, variety, change of direction?
About the Nadal DTL: it's extremely frustrating to watch him play realizing how much shorter points would be if he could hit this shot with confidence. However, his passing shots are rivaled by a select few through the ages, and his crosscourt finds angles and pace that can be ABSURD. His slice, however, hasn't been worth much since he's come back - it was quite nice when he was no. 1.
Also, tangent: is there anyone who hits a crosscourt-rally-breaking-down-the-line shot on either wing with the seeming ease and awesomeness of a peak-Djokovic? (well, maybe Federer)