Not difficult to apply, but definitely a two-man job to ensure accurate alignment before pressing firmly to secure. It doesn't take long to become accustomed to their presence.
First test (after a week of dry weather) was during an absolute downpour yesterday! Window open about 2-3 inches (i.e. below the lower edge of the deflector) yet not a single drop blew in - what a difference compared with the naivete of LR designers whose blatant disregard for the owner's choice to drive with a part-open window is an insult.
In brief: it works.