Solid review, I think it can't really be considered aside the conventional AIO's as you say, it has a different appeal and without lights or flashy adornments it does come across well. My favourite touch to pick up on would be the amount of details revealed in the instructions, not many people will give you an exploded view of their product and that's something that modders will really appreciate.
Just something to note in the silence front I can definitely differentiate between when the pump is running at 7 or 12v and I would never describe it as being totally silent, but considering it's in a Parvum it does extremely well. Infact it humiliates the H105 in that respect. Running out of a system with no solid surface to resonate against like you say it's genuinely hard to tell whether it's on. I thought my PSU had died when I was bleeding it lol.
The mounting system isn't the worst but I still prefer the traditional stand off and thumbscrew approach, I wouldn't rate it in that regard as you have to apply pressure while aligning it and the backplate can get pushed away. (I'm not prepared to stick anything to my motherboard though)