Yeah, there are definitely a few, I've implemented an experimental thing that removes titlebars for windows, but that's totally dependant on the application it works on, so browers that do fancy things don't work as well, but something like notepad/cmd/etc... work pretty well.

Also the focus bar is a little overlay line that could be improved, but it's very difficult to make it like in i3wm without covering a significant portion of a windows content since you can't really control a windows rendering, etc....