I just finished reading Dean's Kite of Stars and Other Stories and it's a diverse collection of stories. I was talking to Dean about it during LitCrit and pointed out that one problem I had when looking at the table of contents is that as a friend and follower of his work, it's honestly not as huge and exciting for me. The problem of course is familiarity. Half the stories in the collection, I've already read in some form or another. And this just doesn't apply to Dean but to other authors I'm following. I love Jeffrey Ford's work and I have both of his short story collections, The Fantasy Writer's Assistant and The Empire of Ice Cream. Unfortunately, I skipped a lot of the stories in the former simply because I had read them already from other sources such as the Year's Best Fantasy and Horror anthology. I really appreciated The Empire of Ice Cream mainly because at the time, I decreased my reading pile of SF&F work so discovering his new stories in that collection was a real treat.
What more with mainstream authors? I mean I love Neil Gaiman but as a reader, when I buy his collection like Fragile Things or M is for Magic, there's a decrease in enthusiasm because he's so popular that most likely, I'd have read most of the stories featured in those collections. (It's actually recommended that you live in a cave before picking up those books.) China Mieville's Jake and Other Stories was a welcome surprise mainly because I don't follow the author as extensively (his writing isn't endearing to everyone).
How about you? Do you feel the same experience when reading short story collections? That's why for Dean (and me), he looks more forward to anthologies. Because you're not just exposed to one author but a gamut of writers with (hopefully) different writing styles and techniques. I also think it's more likely that you'll fall in love with more stories in an anthology (where each author supposedly showcases their best stuff) as opposed to a collection (where the "stronger" piece of the author might overshadow the rest of the stories). Of course I don't have data to back up that conclusion aside from my own experience.