Got my E-M5 back from Olympus, good as new, only 7 days after I mailed it. They replaced the shutter, gear case and the screen frame. The screen frame was a recall: they always replace them on E-M5's of a certain vintage.
What seems to have happened is that a cheap aftermarket battery failed and expanded, putting pressure on the shutter gear case, causing it to jam. The battery was at least a millimeter bigger around the center and it really didn't want to come out.
Anyhow, it's all good now, and I'm super happy with both the cost of the repair ($165.88 plus tax flat repair charge including return shipping) and the speed and quality of service. It's nice to know that this kind of service is available from the OEM at such a reasonable price. I've since tossed out my aftermarket batteries and grabbed a couple of Olympus replacements.
In terms of the E-M1, the increased dynamic range and sharpness are noticeable, at least to me. However the E-M5 appears to have better low light performance, especially at 200-6400. While the E-M1 handles much better with large lenses and strobes like the Panasonic 35-100 and Olympus FL-50, I'm much more comfortable with the E-M5 when used with smaller lenses like the PL 25mm f/1.4 for the Samyang 7.5mm fisheye, my two favorites.
The Panasonic 35-100 f/2.8 is also really growing on me. I knew I'd get a lot of good out of a sharp medium telephoto and this one is just out of this world. I pointed it up and took a quick shot of the moon while it was still daylight at 100mm, f/2.8 and ISO 200. When I proceed it, I cropped it down to 1/2 its original width and height. I'm very happy with this result.