I wrote an article for Flyer a while back about what was available and how to get the best out if it. I am going to do a flight test on PF as soon as it has the mode C side sorted.
No direction indication is not an issue. See and avoid is 8 times more effective if you know there is traffic in your area and miss something by 500ft and you have missed it. I am talking VFR only, the devices are intended to assist see and avoid not replace it.
Rod1