Right...the Nightpro is "loose" with it's wide, overlapping bands for any surgical purpose...but with more subtle boost/cut use, it's also less damaging than a tightly-focused surgical equalizer.
It's major flaw IMO is the lack of stereo coupling and stepped pots, which makes stereo matching a lot of work, so using it on a 2-bus is not very easy, but workable with some tones for level matching each band.
The Air Band (2.5, 5, 10, 20 & 40 kHz) and the Sub band are the most usable for 2-bus purposes.
It's certainly not a mastering grade equalizer, but like any decent EQ, it has it's uses, and most agree that it's "musical" (an overused term), which I guess means it's not nasty or rude sounding in any of its settings and when used for gentle tone shaping.
AFA the shorter lifespan of NTI (and you may have the better info on this, Fletcher), I think it was more due to a lack of serious marketing and them being a small company. So because of that shorter lifespan, there were not thousands of units making it out into the hands of users, though there are some that still use them and really love them (I believe Dave Reitzas is one engineer who uses his Nightpro EQ quite a bit), and people mostly praise the quality and the "easy/gentle" way it treats the music, and the overall opinion is that it has a quality build.
There was a nice writeup in Sound on Sound back in 1997:
NTI Nightpro EQ3D
I got mine around 2001, and I noticed a slight difference in output between the two channels. They told me to send it back and agreed there was a 1/2 dB difference, so they sent me a new unit with perfect matching channels.
I think that they were closed down soon after that.....BUT.....
...they are back now as Maag Audio. The sons of Cliff Maag (founder of NTI/Nightpro) have come together to bring back a quality EQ and preamp under a new company!
Maag Audio | AIR BAND™ Mic Preamps and EQs | PREQ4 EQ4 (500 Series)