I've had a transponder for eight years. What it doesn't do is keep away general aviation and some military - I have had close-up views of a few light twins in the past couple of years. Some sort of PCAS device will help with this.

If you are flying with more than a handful of gliders, Flarm is very useful. For fun flying, perhaps not so much, but for team flying and contests it's a great tool.

I've already heard about the superiority of LX Flarmview, but the Butterfly display came with my core unit.

Mike