I've had a number.....1 in 40 hours sounds about right, I had one during my PPL which was opposite direction, about 100m right, same level......
I was flying a G1000 aircraft with Traffic display in the US a few weeks ago, I realised that the traffic I saw compared to what was on the screen was about 30%....The nice lady informing me of "traffic traffic" went off a number of times......
Sods law says that the traffic is ALWAYS converging......
Damn useful device, shame its not available here...