TIS demonstrated it's worth to me in the first ten minutes I flew with
it. I departed from the radio shop on a hazy day and even though I
was getting flight following the thing showed an approaching aircraft
at my altitude.

I am very happy with my TIS as well, especially in the very hazy
weather in the northeast US. I have a Garmin GTX 330 transponder that
feeds its traffic data to both a GNS430 and an MX-20 moving map.

After almost one year of flying with it, the only two complaints about
TIS that I have are the relatively limited coverage areas outside of
the northeast coastal megalopolis and the inability to adjust the
volume of the lady's voice that states, "Traffic Unavailable!"
Inevitably this alert always comes on just as I am about to touch down
at my home airport and it still startles me.

--
Peter