Not very likely I have had that installed on 02.10 so if that would do any good here it would have already manifested. I'll start the not so fast but much more furious task of checking each config setting manually. Hmm, it seems I'm getting desperate...
EDIT: Now that's interesting.
I've two Fields checked in Display > Fields. Current sort field and Extension (dirs). As soon as I unchecked those two, Opus instantly became snappier. Not as fast as it was, but definitely quicker. What's even funnier, it seems to be gradual. Unchecking only one of them only makes it slightly faster. Restoring the Fields page to its default (regardless of the fact that I had made changes to no other items there ) will make it even faster.
Restoring defaults to Display > Colors and Fonts too gets Opus back to (almost) normal. There's' one item there that makes a rather significant difference: Files and folders - System. Disabling/enabling that has a drastic effect on eg. scrolling, that is, holding down arrow keys and waiting for the repeat to kick in. Traversing through 23 items in a folder having system files present with that setting disabled takes <1.5 seconds. The same having it enabled it takes >3 seconds and feels pretty sluggish.
I can live with the two Fields settings disabled. However, I'd rather not have my system file/folder coloring lost to this issue. Any hints on what could be done to keep both the speed and the coloring?