Yes, I am. I don't have much experience with playing with lots of different gear in my setup, but what I have gathered is this: The amp section separates channels really nicely... which I mention because the coolest thing about the NFB-28 is how well it images. Like, DANG does it image. I've heard lots of nice speaker and headphone setups, but plugging this NFB-28 in preamp mode into a NAD 356BEE's power amp section, I could almost see the instruments on stage. I listened to the John Mayer Trio's live recorded album "Try", and within about 15 seconds I remembered mental pictures of the whole stage and how each player was setup, and then I just closed my eyes and followed Steve Jordan's fills around his double kit with ease. Really cool.
As for a sound signature, it's just smooth enough to never sound digital... in the DAC, pre, and headphone section. Some call it warmth, some call it darkness, it's neither of those things, and hard to describe. Pairing with a tube amp would not be overly warm by any means. My Q701's can still sound a bit grating, but they are a super grating and dry can out of most sources. In comparison to the Benchmark DAC1 HDR, I think the DAC1 might have better dynamics in the treble, but it's not as natural sounding over the whole range. The DAC1 is a brilliant DAC IMHO, but not for me.
As far as detail levels go/ people's impressions of the ES9018 sound... yes, there's lots of detail and treble extension, but it sounds right, not boosted. I'm not a treblehead, and am actually quite sensitive to a range of it (think HD700 - ouch)... I just think many members here are way too scared of bright treble due to past cans or gear or whatever. The sound is as accurate as you can get without sounding oversharpened or cold or unnatural.You hear what you're meant to hear, and no less. It is a neutral sound with great control in all ranges.
All in all, it's a great jack-of-all-trades, and it gives me confidence that an Audio-GD dedicated DAC would be even better as you're not paying for the pre-amp, headphone amp, remote control, and balanced topology. I think it would be safe to bet that the NFB-3 could perform at least as well, if not better (I'd expect a blacker background, which would probably fix the treble microdynamics and open up the sound even more in the mids and bass). As a final note, Audio-GD's latest products are all buzzword friendly and can handle high sampling rates and DSD, so you'd be future proofed for a while.
... but the implementation of chip and the analog section are much much more important than the chip in most instances. You could always get an Audio-GD Compass 2 and different DAC modules to test for yourself 
