Select transparency when saving GIF or PNG: In Irfan appears small copy of the image and I was able to choose color directly - just pick a pixel with color what I want to be transparent. I think this is very comfortable

In fullscreen I miss more freedom with mouse - IMO next/prev image is ok just by mousewheel; buttons should be more useful - like in non-fullscreen mode (moving, selecting...) Please is problem to make scrolling by method "onkeydown" instead "onkeypress"? This is in ACDSee - it's more smooth and without any delay.
Except that is XnView perfect and excellent, many thanks, Pierre!
Thanks for reading and answering.