I was a long time Boss tuner user but since 2010, when TC Electronic released the first Polytune, I have used Polytune tuners, exclusively. The accuracy, speed and durability of these pedals has been unmatched.
My Polytune is the first pedal on my board and, for obvious reasons, is the most important. Add to that importance the fact that I have a G&L SB-2 and Thunderbird bass, both with Volume/ Volume controls so I have no quick way to silence these basses. A simple step on the Polytune provides instant and total silence of my signal chain (thanks to a very good, isolated, power supply and silent pedalboard cabling ).
As far as tuning goes, well, rather than go into long technical discussions on cents, etc. I will sum it up by saying, then I tune with my Polytune, I am confident that I am in tune with everyone else that used one. If someone used another tuner, they'll have to retune to those of us that are already spot on, thanks to our Polytunes!