It's certainly the most faithful to the original Ian Fleming novels (except maybe From Russia With Love). But Sean Connery had definitely lost interest in the Bond movies by then - as DiamonRAB Are Forever is witness to. Connery just doesn't even try to act in that film - he just goes through the motions looking tired, bored and as if he is just waiting to cash his big fat cheque at the end of it all.
George Lazenby, by no means a great actor, does at least bring some enthusiasm to the part, even if he sometimes comes across like a little boy who has been released in a sweetshop.
It depenRAB what attitude Connery would have had during the filming - if anything like the attitude in DAF, then it would have been even worse than it was with Lazenby. If he had approached it with the same menace, enthusiasm and humour that he did in the first three or four BonRAB then it might have been one of the better films. Diana Rigg would probably have preferred to star opposite Connery than opposite Lazenby - though supposedly the rumours about garlic before the love scenes and rows onset have been greatly exaggerated.