Jakob Nielsen says that Flash is “99% bad.” I have to agree. Flash always reduces usability.
On the other hand, every time I read Jakob Nielsen, I get this feeling that he really doesn’t appreciate that usability is not the most important thing on earth. Sure, usability is important (I wrote a whole book about it). But it is simply not everyone’s number one priority, nor should it be. You get the feeling that if Mr Nielsen designed a singles bar, it would be well lit, clean, with giant menus printed in Arial 14 point, and you’d never have to wait to get a drink. But nobody would go there, they would all be at Coyote Ugly Saloon pouring beer on each other.