I know it's an old thread but I thought I'd share my experience after coming back from hols and giving 3lb nanofil a decent workout over a week.
The Good: casts like a dream and really zings through the guides
The Bad: lots of wind-knots! I used 3lbs fireline crystal on the same outfit before the nanofil and didn't have any wind-knots but with the nanofil, I had at least 10% of wind-knots!!!
The Ugly: the line broke twice for no obvious reason! The first time on strike but I got lucky and the line got caught in branches, so I got the fish and more importantly $17 of lure back! The second time, I couldn't believe my eyes as I saw a 5 cm piece of line fly of the reel, and then a second later my cleanly cut line disappear through the guides!!!
Now as I said in the "Good" section, when it works it really casts like a dream and also I had no problems with knots (btw the stuff is reaaally slippery) or landing fish (up to 50cm flatties), but when it doesn't work, i.e. wind-knot, it's really a joy killer and I can't wait to try fireline exceed instead. I'm also a big fan of microfuse but it looks like it's been discontinuedand sadly my beloved SOL 2000 which was spooled with microfuse went for a swim and never came back...
So that's my feedback, fireline still rocks and nanofil (in the 3lbs) sucks big time!