The OM-D E-M10 will be, at $799 with the kit 14-42 lens, the least expensive of the three OM-D's.
Olympus has had to compromise to reach that price point. The M10 is not weatherproof, and it's in-body image stabilization is only 3-axis rather than the innovative 5-axis system in the more expensive OM's, but it has the same "Adaptive Brightness" feature in the EVF that the top of the line M1 has. It will crank up the viewfinder brightness in bright sunlight, but dim it automatically as the sun sets so you won't be blinded as you shoot into the evening.
The M10 also has wifi to enable on-the-fly image transfers to your phone or laptop.
There's an typically enthusiastic story on Steve Huff's site.