I use it on my tablet and it direct plays all of my (limited) media, and also handles and organizes downloads to the device with reencoding options. Playback is more reliable compared to Swiftfin. (Edit, it messed up some subtitles that run fine in all the official apps) UI seems modeled after existing streaming services.

They also have a plugin that “updates” your existing Jellyfin install so the features show up on the official client, but uses code injection which I didn’t like and so did not partake. The sense I get is that they push for features and implementation while official Jellyfin development takes a much more conservative approach. I hope they can work together some day.