I never really managed to figure out the OpenJDK story apart from that it is what gets included in Linux distros and it sort of works. Read not too great stories about its performance in the past, am not exactly sure about its compatibility (it seems to lag behind a bit), Windows support is a whole complicated story of its own... Call me ignorant, but at first glance it doesn't look attractive. On top of all that, indeed Oracle being involved with development at all, together with their reputation of being a legal hothead.
Not mentioned in my initial post, but I also like to keep my code portable between server and client. Firstly, there's no way I'm going to require clients to have Java installed. Secondly, a truly native GUI is practically impossible, so I would already corner myself into needing a second language anyway.
OpenJDK performance has been closing the gap with the Oracle JRE over time. One big gap was different graphics renderers but this is being fixed in Java 9 (possibly earlier).
Java 8+ has a "javapackager" tool that makes native installers/packages for each platform which contain a bundled JRE. So your users no longer need one installed themselves. And finally SWT lets you use native widgets if you want them.
Not mentioned in my initial post, but I also like to keep my code portable between server and client. Firstly, there's no way I'm going to require clients to have Java installed. Secondly, a truly native GUI is practically impossible, so I would already corner myself into needing a second language anyway.