I bought this tuner on July 1st 2015. It arrived amazingly fast, in less than 24 hours from Germany to the Netherlands!!
I bought the tuner to use for (intonation) practice on double bass (bowed). I also have a Korg CA1 tuner that is very good and reliable but this has not illuminated display which can be hard to read sometimes. It also is not the fastest tuner and not a clip-on (mic).
The Polytune clip does have very good visible LEDs. It also appeared to be very fast looking at the video's online. It tried it on one of my guitars and it works just fine in all modes. And yes, it is very fast.
But... on double bass not so much luck... The tuner has some difficulty picking up the signal from the E string. It does seem to work when plucked but when bowing it just does not work very well. On all other strings it works fine (in both guitar as well as bass mode).
I use the tuner on the bridge of the double bass so I can look at it when practicing scales etc. Being almost horizontal the tuner cannot decide its position so it frequently switches orientation. Of course this will not happen on (bass) guitar but it would have been nice if the gyro could be disabled.
And the final thing.. I read in the manual that the Polytune switches off automatically after 3 minutes to save the battery. I, mistakenly, thought that would be after the tuner had not been USED for 3 minutes. But this is not the case so it shuts off in the middle of a scale.
The build quality is OK. The plastic looks a bit flimsy, it would have looked so much better in stainless steel. The clip works fine and the display is very bright.
All in all the Polytune clip on is not exactly what I expected from it. Of course this is mainly due to the way I want to use it (not just tuning). I will give it another chance during a longer practice session to decide whether I'll keep it or maybe return it
EDIT: after just two days of careful use at home the rubber of the moving part of the steel clap came off. When I finally found it again on the other side of the room I noticed the rubber being split in two on one side. This should not happen!!