Awful. The OS maps OA have given me access to instead of the many Viewranger maps I paid for don't render clearly at all zoom levels. And when I zoom out further I can't see the 1:50,000 map as it switches to a very low resolution road atlas. I can therefore only see a radius of about 3km from my location at 1:50,000 which isn't enough to use it for map reading while cycling.