It has a large amount of information about you and hence I cannot trust it. I did download it once but removed it before registering myself.
Many of my friends do use it and I myself use it for my work number where I get calls and it helps if I can speak on a friendly note, but not for personal use. My work number is also stored a "XYZ" so if I am calling someone and they use TC, they know who is calling. Helps to get business a lot.
But I do not trust the app at all as you can see everything can be hacked and Tc is not different.