These things are tiny, and packed with features. On top of that they are very user friendly. It can be mounted a variety of ways and adjusted to make it easier to read. They are chromatic meaning they can read any note, this is important because I use different tunings at times and I can't stand tuners that only recognize the 6 strings in standard tuning. The lights change color depending on how close you are. Green is dead on while yellow and red means your getting away from being in tune, pretty simple. You can see the mounts in this picture and they are very easy to use, the tuner itself can swivel or be taken off and mounted on the D'Addario Artist Capo which I've found pretty helpful. There is also a blinking metronome. Like I said lots of features. Plus with the 2 pack one stays on my main guitar and the other on my Artist Capo.
The tuners are very accurate and fairly quick. They are small enough you can leave them on the guitar when you place your guitar in a case or gig bag. I was wondering how well I'd be able to see these tuners on my guitars that had tilt back headstocks but it's not a problem at all. In comparison to other headstock tuners one thing I really like is that the clips don't leave a mark on your guitar. A friend of mine left another brands tuner on the headstock of his guitar and it left an indent on the finish! These will not do that. Also the battery in these things are a standard battery similar to what is in a key fob.
So how does it compare to the TC Polytune? Well I don't have to pull out my pedalboard if I want to tune my guitar but the Polytune is faster, we're talking slightly here but it is noticeable. Also the NS tuner is not great with down tunings. Lately I've been tuning one of my guitars down to Drop B and the NS tuners seems to struggle with anything under D. But there is a work around, simply fret at the 12th and the tuner works fine. Also I personally find the blinking metronome worthless. I tried it but I miss the clicking sound. Once again not a big deal I just don't use it. These things are not big issues, I'm sure as the technology gets better these things will be addressed. If your looking for an easy to use tuner check out the NS Microtuners from D'Addario.
This review was completely unsolicited and any opinion is my own.