High ISO test by DecQuinas, on Flickr
ISO 4000. Was under pretty harsh lighting conditions (only light source was two yellow lamps).

Still pretty impressive IMO. Although my friends face is a little "burned"...
Anyhow, I think the weakness of the X-E1 (or the X series line up without the new lenses in general) is that the focus hunts alot in low light. Never shot during the day yet with the X-E1, but currently I've been facing focusing issues in low light conditions and that annoying aperture sound of the lens. EVF lags when trying to focus in low light too (framerate drop).

But still a great camera... Really like the lens too.