Several folks have reminded me that Howard Hughes is said to have granted permission for the filming of Diamonds Are Forever on property he owned in exchange for, among other considerations, either a 16mm print of the finished movie or (accounts vary) 16mm prints of all the James Bond movies. So he presumably saw Diamonds. We just don't know what he thought of the way the character based on him was portrayed.
Y'know, I find it amazing that the filmmakers got permission. They had to submit the proposal to Hughes' underlings, all of whom were notorious for being terrified of what "the old man" would think about something. Hughes was already somewhat irrational by that time, especially about his privacy and image. This was the period where Hughes would hear that some journalist was readying a book or article about him and he'd call one of his lawyers and say, in effect, "Stop publication or you're fired." If I'd been a Hughes aide at the time, I'd have looked at the script, saw that it included a Hughes-like figure and thought, "Even if the boss okays this, he might hate the finished film and sack everyone who didn't stop it. There's nothing in it for him (or me) so I'd better stop it." But somehow, that isn't what happened.
The arrangement presumably was to allow some filming at the Landmark Hotel. As far as I know, the hotels where the movie was shot were Circus Circus, the Riviera, the International and the Landmark. Of these, the only one Hughes ever owned was the Landmark. (He also at times owned the Desert Inn, the Sands, Castaways, the Frontier and the Silver Slipper. The only one still standing is the Frontier and no one's betting on it being around for long.) The "Whyte House" — the hotel in the film owned by the Hughes doppelgänger, Willard Whyte — was played by the International, which Hughes never owned and which is now called the Las Vegas Hilton.
Scott Blacksher writes with regard to that story I related of Hughes buying TV station KLAS and phoning in to tell them what late movies he wanted to watch each night…
I've spoken to a couple of life-long residents of Las Vegas about things they remember. The funniest story was about how Howard Hughes kept falling asleep while the TV station ran Ice Station Zebra. Whenever Hughes dozed off and reawoke he'd have his people call KLAS-8 to put the movie on the last scene he remembered watching. It wasn't unusual for Vegas to watch the same segment of a movie more than once.
Talk about Video on Demand. I recall talking to one Vegas resident who recalled those days as rather exciting. Every night, he'd turn on KLAS and find some great, surprise movie run uncut and without commercial interruption. This was before home video or HBO so unexpurgated movies on your TV was a big deal. (I remember when we first got cable TV at our house — the legendary Theta Cable with its "Z Channel" — we'd watch anything. It must have been like the early days of talking pictures.)