I've been reading William Tenn's stories since I was a kid; his stories were scattered through a bunch of the anthologies on my father's bookshelves. (I know that "William Tenn" was only his pen name, but it's the name I've known him by for most of my life, so it's the name I'm using here.) Finally read his novel Of Men and Monsters in '97 or so. Picked up the 2001 NESFA Press two-volume "Complete SF of William Tenn" (Immodest Proposals and Here Comes Civilization) a while back; possibly at WorldCon 2004, where he was a guest (and it was neat to finally see him in person). Sadly, have not yet read those volumes (the bits I hadn't read previously), but still plan to do so.
Just read his story "Eastward Ho!" a couple months ago, possibly for the first time, and blogged a quote from it that I had enjoyed.
Wikipedia has what I think is a widely quoted bit of praise for Tenn from Theodore Sturgeon:
It would be too wide a generalization to say that every SF satire, every SF comedy and every attempt at witty and biting criticism found in the field is a poor and usually cheap imitation of what this man has been doing since the 1940s.
(It goes on from there, but that was the line I liked the best.)
Phil Klass/William Tenn died this morning, age 89. His official web page has more about him, including links to various people's eulogies and remembrances.
A couple of those pages link to a radio interview from 2002, apparently featuring his own reading of his story "On Venus, Have We Got a Rabbi!" I haven't had a chance to listen to it yet, but hope to do so soon.
I'm sad to see him go.