People talk about conflict in novels all the time, and for good reason. Conflict is what keeps readers reading. They need to know what happens next; they have feelings of anticipation or fear or anxiety. I think people get so caught up in creating conflict - creating dissent, enmity, barriers, challenges - that they forget that while conflict keeps people reading, treats are what make readers remember a book fondly. Especially in romances; I never hear anyone say that their favorite romance novel is X because of Y painful, traumatic scene. You know what I do hear? "OMG, you have to read X because of this awesome, hot scene...."
To give a very local example: at least three people have said to me, "You have to read Tessa Dare's Goddess of the Hunt because of this closet scene." And they were so very right. The closet scene. It's the first thing that pops to mind when I think of that novel, and it's a pleasant recollection.
Charlaine Harris, whose talent is mind-boggling, can do it with two words: "gracious plenty." If you say "gracious plenty" to just about any fan of the Southern Vampire Mysteries, the fan will know exactly what you mean, and that fan will sigh, or squeal, or stare dreamy-eyed off into the distance, wishing herself in Bon Temps.
Now, if you know the Southern Vampire mysteries you know that plenty of authors have tackled the subject of a "gracious plenty" but never so quotably, and never with such charm. The phrase, and the scene it's a part of, is a treat.
It doesn't have to be a sex scene, although sex scenes are likely locations. Jennifer Crusie can elicit the same reaction with dialogue. And treats can evoke a lot of feelings, as long as one of them is a warm-fuzzy. The birthday cake scene in Karen Marie Moning's Fever series is a good example there - it rips your heart in two and gives you a warm-fuzzy, at the same time.
I think of them like a trail of breadcrumbs, little rewards to the readers for bearing with all the stress and anxiety that the conflict causes. When I'm writing, I'm always asking myself: how can I take this scene, as crazy at it is (OK, so my heroine has been kidnapped and my hero has just rescued her...), and make it feel special? The characters need to jump that bar, rise above the melodrama. The baseline, the story, isn't enough. If a treat is done right, the feeling of romance dwarfs anything plot-related.