Regardless of your current equipment, you should find it an interesting camera body.
Highlights for me:
- 1/8000th of a second shutter speed
- Tilting electronic viewfinder (EVF)
- 2 axis in-body image stabilization
In the old days of medium format, they used a vertical viewfinder with the upside down image and all and that was more fun than you could imagine. Somewhere along the line (the Mamiya 645 1000S, perhaps?), an eye level viewfinder was added.
Not all your subjects will be at your height and getting a good angle is usually critical to the success of the photo. Of course, if you're not as tall as your subject, tilting the viewfinder up won't help you much.
Having the flipping (no expletive!) display panel on the rear helps greatly, so in bright light and macro settings, a 2.7+ million dot/pixel/whatever viewfinder will help.
Given that Voigtländer and others have already presented f/0.95 maximum aperture lenses, using them in bright light without a quick shutter speed has limited their Depth of Field advantage. Olympus recently added a 1/8000th of a second minimum (not maximum--it's quick, not slow!) shutter speed, it seems right that Panasonic should do the same. That leaves the Olympus E-M5 and the Panasonic GH3 out of luck, behind the times--oh, no!!
Considering that most micro Four-Thirds lenses from Panasonic and Olympus have small maximum apertures, it wasn't really a problem, but Panasonic revealed that the (Panasonic/Leica) 42.5mm f/1.2 lens is on its way--at an undisclosed time and price. Add that to the Panasonic/Leica 25mm f/1.4, and you have more need for the 1/8000th of a second shutter speed. I have frequently used such a shutter speed with the Four-Thirds version of the Leica/Panasonic f/1.4 lens. (If you're tried the Four-Thirds Leica lenses, you know why I make the distinction.)
My GH3 is feeling a bit anemic these days with all these enhancements in the world but it still works as well as it did when I first got it. Obviously, for stills, it wasn't the greatest choice, but for overall handling, it's the best. I never could have handled the E-M5 as well and got work done quite so easily. Similarly, the E-P5 and the GX7 will be great tools, but not for me. Even when I'm casually shooting, I have a big camera body and big lens. I sometimes hang the GH3 around my neck to get a different angle on things, but for fast sports, it's not great, and for casual stuff, it's overkill.
I think people will love the GX7, as much as other people love the E-P5 but they'll adore not forgetting their clip-on EVF.
How does this all change with the E-M1? It doesn't change much since the E-M1 and the GH3 are more the opponents. Still, the 1/8000th of a second shutter speed will help with those Voitgländer lenses and the GH3 doesn't have it (and that Mamiya 645 1000S added 1/1000th like the 135 format SLRs of the 1970s). The GX7 likely has better video than the E-M1, which doesn't even seem to consider PAL 25/50 timing.