And it occurred to me that I would buy a book like this if I saw it on the shelf.
That's not as arrogant as it sounds--it just means that I've succeeded, at least in that scene, in meeting one of my writing goals: enjoying something I've written as a reader. That's a great litmus test for whether a scene is "working" or not. Take off your writing hat and put on your reader hat to see if a scene passes muster.
I think it's important that writers become fans of their own work. That they occasionally have the thought, "Hey - I would actually pay money to read that!"
Also, becoming a fan of a specific scene tells you whether you're on the right track. If you get so absorbed in the characters and the story that you "forget" to edit? Well, that's a pretty good sign that you're doing it right.