Dreadful. The content is great but everything else is awful.
My credentials didn't work for the first few days, the password reset did not send an email, and tech support took a few days to respond. Support then responded multiple times as if I was a new customer each time. Streaming quality was bad including a movie that had a long high pitch whirling noise throughout which gave me a migraine. If you watch part of something the app does not keep track of where you stop so I had to write down where I was in something I was watching. Watching tv shows was unbearable because the episodes I watched were not marked nor was my progress recorded anywhere. So any time I went back to anything I had to guess which episode and then scroll through to find my place often spoiling things for myself from later parts or episodes.
The worst part is that all of this content is so interesting and I loved every documentary I watched. It's awful that I would rather watch bad uninteresting things on a different streaming service because the Sundance Now service is terrible.