This thread will eventually rival the car tire threads in its usefulness to the general community. By adding my two cents, I'm proving that I don't have a lick of sense, and so maybe the fact that I don't have the FZ-1 mirrors should be taken as a data point in their defense.
In any event, I am not a svelte guy, but might be considered to be width challenged. I don't have any trouble seeing directly behind me with the stock mirrors. I first mentioned in 2008 that I liked the stock mirrors quite well, and was the victim of the usual "teaching activity" that many forum members are only too happy to apply (about the head and ears). I have run 12 new motorcycles through my stable since 2006, and a few used ones to boot. The FJR mirrors may not be the very best I've seen, but by my standard, they are quite good.
FWIW, I've always thought that the reason some don't find it necessary to switch to the FZ-1 mirrors is because they have opposable thumbs and can adjust the stock mirrors to perform quite well.