Well, he wasn't bad, but he wasn't great either. I just wish he had done a couple more movies to grow into the role. They asked him to, but he refused (and later regretted it).
That said, On Her Majesty's Secret Service is my favorite Bond movie... Great action sequences (the ski chase), the lovely Diana Rigg, and one of John Barry's best musical scores.
You're right about the music, ecurbh, some of it was striking.
It was one of Fleming's best 007 novels IMHO. And it was a great bond movie, mainly because it didn't have as many absurd gadgets, it DID have the lovely Diana Rigg, and it was one of the best-written of the Bond screenplays. Still, Lazenby's performance was extremely weak.