Monza, while I am not Terry, I have owned the other cameras so I can render a personal opinion. If I had to rank UI's it would go like this:
1. Ricoh GXR
2. Panny GF-1
3. Sony NEX 5
4. Oly EP-1
However, it is really close between the Panny & the Sony. It depends on how frequently you change ISO settings. Further, it depends on how often you would use special features like panorama or HDR. I have found the Sony pretty easy to use as I don't change ISO that often in normal shooting (not testing for ISO performance). Changing aperture or shutter speed is pretty easy and fast on the Sony as is changing exposure compensation. Formatting a card is a bigger problem because menus don't wrap and it is near the bottom of the menu.