Beaumont was one of the best of his generation, in my opinion. He was good both with prose fiction and screenplays (in general; his adaptation of The Case of Charles Dexter Ward for The Haunted Palace was... lacklustre to say the least; but then, he never made any bones about not being a fan of Lovecraft), and even when he took liberties (as with The 7 Faces of Dr. Lao), he somehow managed to make it into very memorable material.
Ellison, by the way, was good friends with him, and a great admirer of his work. He has credited Beaumont with the two most valuable pieces of advice he ever received about working in Hollywood: Don't give up your other writing. As long as you continue to write other things, they don't own you, and will see you as a prince from a far-off land. And: Working in this town is like climbing enormous mountain of cow-flop to reach the one perfect rose at the top: Once you have made that hideous ascent, you find you've lost the sense of smell.