Wandering around the house this morning, trying to avoid writing, I plucked an Alfred Bester collection off the shelf and started reading at random. I fell into an essay from F&SF in 1961 where Bester evaluates some of the top SF writers of the time. He compares Heinlein to Kipling in terms of both virtues (craftsmanship) and vices (oversimplification of reality, xenophobia), then continues:

Despite these flaws, Mr. Heinlein remains the most powerful and original force in science fiction today; an author always to be reckoned with, never ignored. In fact, the latter would be impossible. Mr. Heinlein reaches out, takes the reader by the scruff of the neck, and doesn't let go until he's shaken the wits out of him. Some day we hope Mr. Heinlein will use his talent to shake a little wit into the reader.