The flip screen on the OMD EM5 is actually fairly limited in functional range: you can go up and down but not left or right. I don't use it that much, but I have used it a few times to get shots that would have been difficult otherwise.
Macro is an obvious use for flip screens, but one that people overlook is using it for framing for wide angle crowd shots.
Here's a practical example I got as a front page of a newspaper for Black Friday. I wanted to show all of the crazy lines at the local Target but to do that I had to get behind a display where my vision of the whole scene was blocked. So I had to raise my camera (K20D and 16-45 f/4 at the time) above the display and take a photo of what I thought was there, chimp, then retry. With an articulated screen I could have framed much more precisely. Holding your camera up high with a wide angle is a great method for showing more of a crowd off (say at a political event) if you can't reach a higher vantage point in any other way.
If they can add an articulated screen while keeping it weather sealed I think it would be a welcome addition. Not a make or break one, though, for me personally.