We tested our RX100 for the first time for video. All footage was shot at 1080p60 handheld. We see less aliasing and moire than from the NEX-5n/7.
We used out Zacuto Z-Finder as a loupe. Looks funky but works.
This provides a very large viewfinder image. The image stabilization on the RX100 works fine. Too bad the RX100 does not feature a ND filter.
Have a look at an alternative way to use the RX100 for video.