The progress panel for copy shows up only after some time (a split of a second) - I know this is not to show it completely for quick operations, but the result is WinSCP seems slow or non-responsive. I would like the old behavior back, probably as an option.
New icons - I like the old ones style, and the new icon set is really stupid. Also, I now have to search for the icons I used to know well, like Refresh, in order to do basic actions. Is it possible to select any icons via settings? I could not even find the new icons in the exe's resources using ResHacker.
Overall I'm disappointed with the interface changes in the new version 5.5 and looks like you had nothing to do but mess up what already had worked fine :)