The transition is perfect from silent picture to sound: the glass, the dog barking, the laughter, the dancing, and - finally - the dialogue. It's a perfect message. Keep moving forward and respect the past, the foundations of your craft, as you go.
As effortless as they make this look, it was weeks of rehearsal and days of exhausting filming to capture this magic. But when you see it on screen, it was all worth it.
In a Hollywood just as Greta Garbo was rising, Valentin's thick French accent would make him somewhat fearful of how people would cast him in reaction to his voice, now wouldn't it? It's a nice hidden depth to his stubbornness if so.
What a wonderful finale this was. I saw it several times the year it was released, and the audience applauded every time. How often does that happen in a cinema?