Is the NHT xd System worth buying today?

Too late for the OP, but I wanted to reply to the comment about mains hum.

I believe what Stereophile documented was the self-noise of the system, not mains hum.  Mine don't hum, but you can hear hiss if you put your ear to the tweeter.  You'll find similar comments about hiss from some modern active DSP systems (e.g. Dutch & Dutch).

My Xda (the amp/dsp box) did make an annoying mechanical whine (not transmitted to the speakers), probably from the switching power supply.  I sent it in to NHT, and they were not able to fix the issue.

To me, this system is a lesson about undocumented, proprietary DSP systems.  As far as I can determine, If my Xda stops functioning, there's no way to repurpose the digital crossover filters.  Updating the amps and the DSP is also not an option without considerable hacking, or creating your own crossover filters from scratch.  

I hooked mine up last week just to remind myself why I was dissatisfied.  Surprise, they sounded great.  The very even dispersion means they can really float images beautifully, better than my Vandersteen cloth Quatros in this regard.  And though I never got the second bass module, the bass clarity and weight in my room was satisfying.  This makes me wonder if I took the wrong path for my room with the floorstanders.