but I also tend to get jumpy when I see websites or brochures that are too slick, particularly if it's for charities
That's indeed another side of the coin. I am associated with a fairly large charity that flies with sick/disabled children all throughout the Netherlands. Our charity manages to attract professional cameramen, photographers, graphic designers, web designers and so on. The result of this is that our marketing in general (brochures, web site, event reports etc.) is very, very good. Possibly even too good for a charity our size: We come across as far more professional and wealthy than we are. Which reduces the "sympathy" factor and thus donations.