I bought these about 9 months ago, so I've had time to learn them somewhat and get past the honeymoon phase. I'm a hobbyist now, but I ran a small-but-busy recording studio in the past, mostly working with local bands.
TLDR, I have nothing bad to say about these, I think they're fantastic.
I'm using them in a very small, but reasonably well-treated room in combination with the MA1 calibration system. Even without the calibration they're great, but it's a big help in my room, which has some pretty big issues with standing waves in the low and lower-mid range. I'd describe the character of the monitors as 'grey and unexciting, but not boring'.
Long story short, they're terrific. I'm very happy with my mixes and they translate well. I find the monitors accurate and unhyped, and they show me what isn't working. If something sounds 'off' through these monitors, then it's off. If it sounds good, then it probably is. For me, there's a lot less guess-work than I've had in the past. I simply mix so it sounds good on the monitor, no intellectual exercises required. Stereo imaging is great, centre imaging is great, depth-of-field is great.
I also have a single Mixcube to check mono compatibility, mid-range and transient response, but I usually don't have to make too many adjustments after working on the Neumanns. With this setup, I rarely get any surprises after I check on real-world systems (phone, laptop, earbuds, TV, clock radio, etc).
I also check the low end on Beyerdynamic DT880pros and Audio Technica ATHm50s', but I don't find too many surprises there, probably because I tend to high-pass quite a lot.
Less related to the monitors, but one unexpected benefit of my small room is that, if I stand 2m back from my mix position, the Neumann's (surprisingly) are still putting out frequencies as low as 40Hz, which gives me a ballpark idea of whether or not my hi-pass EQs are set right, especially when compared to reference mixes. It's a quirk of my room so won't apply to everyone, but it helps reveal woofiness in the low end.
I've had Yamaha HS50m's, Adam A7X's and Genelec 8030's in the past, but I prefer the Neumanns. For my purposes, I think they're all I'll ever need and I trust them 100%.