"What say you?"

[mid]

Bill O'Reilly ("... he taught English and history at... High School" and he speaks impeccable American English only) in his "Factor [begins right now]" TV show often asks his respondents:

"What say you?"

Any comments on this question from "good English" point of view please? Dialect? Slang? Of course I understand what he means, but it "sets the teeth on edge" anyway.
Am I missing something here? (He decidedly does not!)

[mid]

Sorry about my question. The answer I readily accept is as follows:
"It's used to ask someone "what do you think about this?" It is certainly not as common as "What do you say?" or "What do you think?" or "What is your opinion?" -- but it is idiomatic English. It is old-fashioned and appears mostly in spoken English these days."