x100 and green ghosts
Agreed. I've never seen a sensor bloom / green ghost issue and I've had mine for nearly a year now. I don't normally use an UV filter but I do use a polarizer. I have seen some relatively strong lens flaring and so sometimes use my hand as an extra shield if I'm shooting with the sun in angles to the frame where it might do that.
No worse (and in fact better without a filter) than other wide angle lenses like the 16-35 L lens I had years ago for the Canon.