PCAS works fine
I have had one of the £1,000 units (Zaon) for around 18 months and found it works very well. It gives approx range., approx heading and altitude w/altitude trend, plus an audible alert 'Traffic' in the headset if something is near.
It is a minor pain having to put it in the rental aircraft with wires each time, but there have been enough times it has alerted me to close traffic - which I have not seen before the alert - that I would not want to fly without it.
Of course, you look out as best you can but you are bound to not see some other aircraft.
Obviously it does not pick up everything - only those with transponder on - but I would rather be alerted to at least some of the other aircraft than none of those that my Mk1 eyeball has not spotted.