Although this episode has much to recommend it, in its most important aspect, it was a great disappointment. Admittedly, the writers had an awesome responsibility here, considering that it was to be the resolution of a seven-year plot line, namely, the relationship between Niles and Daphne.
When it first aired, for whatever reason, I missed seeing it. The next day at work, I asked a coworker and fellow Frasier fan how it went. "It was, ...good", he replied hesitantly. Based on this succinct review, I knew what to expect. What he was saying was that although it concluded in the way that everyone hoped, it was not the triumph we needed it to be, all things considered.
The real problem, of course, was that it came down to a judgment call on Daphne's part. She was torn between Donny and Niles. In the case of Donny, perhaps it was more a case of keeping a promise to a good man, but her statement to Frasier earlier in the episode made this more difficult to believe: "I love your brother, but I'm in love with Donny". It should have been the other way around.
In a classic romantic comedy structure, Donny would have been clearly wrong for her and everyone but she would have known it (much like the relationship between Niles and Mel). Daphne's reasons for wanting to marry Donny would have been purely symbolic; Niles being the reality thus symbolized. As it was, Donny was a likable fellow and actually loved and appreciated Daphne. Not exactly a foil for Niles, but rather a valid alternative.
Personally, I was hoping that at the last minute, Donny and Mel would discover that they were soul mates, and in a complete upset, run away together. Niles and Daphne would then be completely free of guilt and responsibility, and left to comfort each other. Instead, it was the beginning of a troubled period, with Donny suing everyone and Mel's humiliating terms of divorce.
Oh, well. In the end, we got what we really wanted. But as for a rating. I think my friend said it best: "It was, ...good".