The characters of Mr. Wint and Mr. Kidd are a pair of assassins, apparently inept at their job, who are clearly a gay couple. This seems kind of daring for 1971. They are always making humorous quips, and their presence makes the movie more interesting.
Diamonds are Forever was received somewhat favorably in 1971. It has a 67% rating on Rotten Tomatoes, and Roger Ebert gave it a favorable review. The movie has several interesting things that happen, and compared to other films in 1971, it might have been above average. However, today it feels so dated and so absurd that it would make a decent Austin Powers parody. With the right attitude one can enjoy the movie because there is some value to seeing old James Bond films to get a historical perspective, and despite the silliness of the film, Sean Connery has a screen presence that makes you want to keep watching.