I have a Russian turret finder I used with my M3 before I got the goggled Summarons. It took me a roll of film to realise it was pointing up slightly so the roofs of buildings got cropped and too much foreground came in.
However, it was a model of accuracy compared to my 45mm Bronica RF645 finder - it is hilariously misaligned. I've learned to leave a lot more empty space around the subject.
Apart from that, I do use the Voigtlander Heliar 15mm superwide finder which is pretty accurate.