I have an ancient one and I find it handy for
potatoes - I can't imagine waiting 15 or 20 minutes for potatoes to cook as pressure cooker does them in a few minutes
beans and anything else that takes ages to cook
I haven't got the hang of jam in the pressure cooker - but marmalade is speeded up no end using a pressure cooker - though my way of making marmalade is a bit idiosyncratic I must admit...
"boiling" ham or bacon - though you need to soak salty bacon before hand as pressure cooker doesn't reduce saltiness of bacon the way normal boiling would
puddings and cakes - but you have to cook them at normal temperature for long enough so that they rise (if it is something like a sponge or ginger bread) - once under pressure it gets too hot for them to rise - though to be fair I am not a great person for cake.
I have also done lambs hearts (which would otherwise take ages to cook) in a basin submerged in the pressure cooker - ie same as steaming in a basin - I stuff them, but keep the stuffing v v dry as some steam leaks as I am rubbish at covering basins properly so I get some steam leaking in and making the mixture damp_
Bet it would boss oxtail as well but I am not desperately keen on oxtail and it seems to be v expensive for a chopped up old tail of a cow, so I haven't tried this.
really I'd use it for just about anything except; boiling an egg, making bread, making sauces and cooking rice, pasta or cous cous. Though I bet someone has made bread in a pressure cooker....