Eh, I admit I'm on the more prudish side when it comes to ecchi in non-pornographic stories, depending on the tone.
If a show is trying to be taken seriously, and includes serious sexual themes or sex scenes, then I can tolerate them, and still enjoy the rest of the show. I'm definitely of the opinion that 90%+ of all sex scenes are pretty unnecessary, though. I can't think of a time where I absolutely had to see characters having sex to believe their relationship had reached a high level, but there are occasions where it helps to underscore a setting, such as in the game of thrones example above, or to reinforce a theme of hedonism like in the anime Speed Grapher, it can be pretty powerful.
If a show is trying to be taken seriously as a mature story, and it keeps throwing in boob bounces and panty shots, I'm probably going to drop it. You can't have your cake and eat it too, and you can't pretend you want to be taken seriously while pandering to juvenile sensibilities. Generally for people who don't understand why it bugs me so much, I liken it to fart humor. Imagine if, instead of overly ecchi imagery, a character just cut a long fart, and then the story continued on its own serious path. the humor would appeal to juvenile sensibilities, same as the random fanservice, and the non-sequitur nature of it may even entertain, but one thing's for damn sure, after the third time it happens you certainly aren't taking the show seriously anymore.
For shows that are more tongue-in-cheek, or more mid-brow and entertainment oriented, it's a different matter. In that case, while I never have and never will enjoy fanservice in my non-pornography, its presence doesn't detract much for me, either. I can ignore it as a garnish on the more entertainment-driven media, and enjoy the parts of the show I do like just fine.
tldr:
Serious show, serious sex scenes= I don't mind the sexy stuff, but it usually does nothing for me
Serious show, juvenile fanservice= actively kills my ability to watch
mid-brow show, juvenile/serious fanservice/sex = I don't mind the sexy stuff, but it doesn't do anything for me.