Played with the E-M5 for some time. I really like the camera. A few things to highlight :
1. The size and weight just right. No complaints there.
2. Black or Silver - both look good. But I think I would get the silver with the black 12-50 lens
3. AF is superb
4. Touchscreen AF appears to be a touch more responsive than the E-P3 (subjective)
5. ISO 1600 is really OK. I shot up to ISO 10000.
6. 9.6 fps (frames per second) is just AMAZING.
7. The 12-50 lens is fully featured - it has video zoom, electronic zoom, and macro mode activation - there are 3 settings on the zoom ring to access these functions
8. The shutter is silent....very silent, in part because of the weatherproofing. Stealth photographers will love it!
9. Fireworks photographer will love this more - There is this function called bulb live-view mode. Basically, this allows you to see the result of your bulb mode on the fly. You gotta see this to know what I mean. Never seen this feature in any camera before.
All I can say is, is there anything that this camera cannot do or does not have?