e.g. I can't understand the advocation of joining on base, sounds highly hazardous.
If nothing else it demonstrates that if such (experienced ?) pilots do their own thing, circuits for others in their vicinity is made more hazardous.
What I don't like about OHJ's is:
When flying overhead, you are essentially head to head with anyone completing the decent deadside and crossing the upwind numbers. Albeit at 1000' supposedly, but you know how some people fly, "nearly 1000'" or "nearly over the upwind numbers. At a shortish runway, say 700m, this puts you a maximum of 700m lateral separation if you cross overhead the downwind numbers.
However, some people descend pretty quick and tight to the runway, other people fly miles out and turn. This puts the opposing traffic in a blind spot (i.e. below your cowl), while you are turning and descending. Very dangerous if you don't have a big picture of what is going on. Especially as you are now all aiming for the same spot - the upwind numbers.
Next you cross over the upwind numbers and you have to look out for people above you opposite direction joining OH, people descending deadside either inside you (if they fly a tight circuit) or coming in close behind and people in the circuit coming from the right (in a LH circuit). Apparently you might also have to look out for people coming up from below too. Once in the circuit you have to contend with people joining on base and final, so your head really has to be moving around.
Now throw into that equation a Thruster microlight, an RV6, a TBM700 and a Cessna 152, all with vastly different performance.
If everyone joined on something like the US 45° join, then faster aeroplanes can overtake safely, of slower aeroplanes can adjust to pop in behind someone in the circuit. I joined on base the other day in front of a motor glider on downwind. By the time I had landed and taxied clear of the runway, he was turning final. If I had joined OH I'd have come in behind him, then had to fly a really wide circuit so I didn't ram him up the backside and I'd have probably ended up outside the ATZ. Joining base, I could see up downwind, and I could see final was clear....much more sensible if you ask me.
Also note that at many airfields, OHJs are prohibited due to parachuting, military airspace, shared ATZs etc....