I haven't had a problem with my cookies here, I just use strong white flour, but I am not sure any of my cookies needed baking powder.
All my cakes turn out fine as well.
I did have some trouble with a batch of chocolate chips that turned out not quite right and a cream cheese chocolate cupcakes, but those were my own stupid measuring faults.
Well, with the cake the top of the salt popped off and I was holding it over the batter. Never again! I was all out of chocolate powder so I had to scrape the salt out of it. It was ok, but not great.
But we have a fan assisted oven, perhaps this is why.