Nano is just a term describing scale. A nanometer is one billionth of a meter. Structures on that scale are described as nanoscale. Nano particle coatings shouldn’t bother you any more than using a microfiber cloth to clean your speakers. It’s a nice label to refer to the proprietary dope they use to stiffen paper cones and tailor driver performance. Sometimes it’s marketing, but sometimes it can also be the correct technical term.
I tend to be resistant to marketing. Salesman give me hives. I’ve only bought 3 pairs of speakers in the last 30+ years so my experience is limited. (Infinity bookshelf, Dynaudio floorstander, Zu Omen DW) I’ve only had the Zu Omen DW for less than a year. I think they’re great - articulate and dynamic. It’s an effort to shut down and go to bed every night. Right now my dilemma is whether or not to take advantage of the 100% trade-in and upgrade before the year is up. I had intended to try a bunch of different types of speakers, but I like these so much I feel I owe it to myself to see how much better they get further up the line. 60 day demo and $1000/pr make the DW a pretty good hook for Zu.