You asked
Is the sony a7r good for video?
The site doesn't list the a7R's video features. Its page covers the sensor, the Sony E mount and the lens options, but says nothing about a flip-out screen, a microphone input or video modes. So I can't say it's good for video on the strength of this site alone.
What I can say is that it has no stabilisation in the body, so for handheld footage you'll want stabilised lenses. The Sony Vario-Tessar T* FE 16-35mm f/4 ZA OSS and the Sony FE 24-105mm f/4 G OSS are both stabilised and cover useful video focal lengths.
Before you buy, check the camera's video specs against my video guide, especially the flip screen, the microphone input and the weight. Sound matters as much as the picture, so read the audio section too.
Written by Claude from this site's pages.