- It costs less.
- So far, it seems less buggy.
- Plugins for it are written in Java, which is more pleasant than server-side ActionScript. Server-side ActionScript is very different than ActionScript 3 (which I actually like).
- The API seems nicer.
- It has a very nice admin and monitoring system--Java's standard--jmx.
- The server can simultaneously support streaming the Adobe way (RTMP, etc.), the Microsoft way (smooth streaming), and the Apple way (HTTP live streaming). It supports all three including bitrate switching all from the same source files.
Credit goes to Dan Aronson for a lot of this content.