With OHMSS, I just love how different it was from the other Bond movies, and that it really was one of the Bond movies that tried to take the franchise in a difference direction nearly 40 years before Casino Royale. It starts out slow, and there are no big action set pieces for the first half of the movie. To me, a lot of the differences succeed.
And from what I read of OHMSS, it sticks pretty close to the novel, to the point in which it causes a few continuity errors, such as Blofeld not instantly spotting Bond, and the safe-cracking machine being some large thing when it was much smaller in You Only Live Twice.