I have a pretty broad array of design experience, everything from two color logos to six color magazine covers to pre-show, in-theater advertisement on two-story tall movie screens. I have never been tempted to get these kinds of filters. I always felt I could communicate the same kind of ideas without them in ways that are more controlled and less "Topaz Adjust - like". I suppose if a client absolutely insisted on it, I could run a tonemap through LuminanceHDR, or do some local contrast work using a hp filter.
I don't think I've ever seen an ad agency that uses these plugins, I have never been recommended I buy them by professors or other professionals and I've never been on a job site that had them installed.
I think when push comes to shove, these filters are popular amongst some photographers, especially hobbyists, but i don't think they have a whole lot of professional use, at least not in the graphic arts field simply because they lack a degree of sophistication.
That said, I do think they might have uses as an intermediate step. I just am not sure that they're worth the money. At least not to me.