I can tell you the the epl1 with the 20mm or the 14-42 does not have the issue with shadows when using the built in flash. Most of the time when shadow accrue with the uses of the flash, is because the lens obstruct the light form the flash. As the flash is to close to lens, and this also cause red eye conditions. With my point and shoot, they put the flash so close to the lens, when I zoom out I do notice shadow on the photo cause by the lens. But that is something I have to live with when using a compact camera. There is no way to get separation form the lens and flash.
The em1 is a mark improvement on what you have, it is a mark improvement on the ep2, which is the same as the ep1, the first gen pens. But out the box, without deploying the flash, it is not as good as the nex in low light.
If you are after low light and shoot mainly the nex is the better system with the kit lens. And while the 16 2.8 is a soft lens, it is a very good range for shooting indoor photos. It is the only prime I can think of that gives aps-c cameras a prime 24mm eq in range.
Super Frequent Flyer, no joke. Ex Patriot and loving it.
Canon Eos 60D, T1i/500D, Eos1, Eos 630, Olympus EPL-1, and a part time Pentax K-X shooter.