JScore seems to be Node.js improved. Check this carefully designed quote:
JXcore comes with a built-in multithreading support that can be enabled on your existing Node.js applications without additional changes... JXcore multithreading may bring aprox. 30 to 50 percent solid performance advantage over Node.JS cluster module. From http://jxcore.com/home/.
I already tried to install it and it does really work. That's all I can say for now, measuring performance and uptime is tricky and elaborative.
So are there real advantages to switch to JXcore and how to make a decision?
IMHO, JXcore is beneficial for below use cases;
1 - JXcore works on mobile phones (iOS, Android..)
2 - It can be embedded by a Java, Objective-C, C, C++ app.
3 - MT(multithreading) is a winner for an application spends more time on JavaScript land comparing to IO. Otherwise, there is no significant difference. MT works very smooth since I was able to use a node-js proxy-server solution multi-threaded without making any change (jx mt proxy-server)
4 - Packaging and compiling. (http://jxcore.com/turn-node-applications-into-executables/)
5 - Some of the most popular native modules come built-in with mt support, so you don't bother installing them on a target machine.
6 - Built-in external memory store and sqlite database server. (This one is a life saver on Windows)
I had a problem also. For example, I needed to disable HTTP header byte size check in order make my application running. For some reason they've added extra security checks by default so you may need to update your application a bit.
Update:
JXcore is now an open source project with MIT license.
I use JXCore to run Javascript from native Java on Android. It can also be called from a background service such as a SyncAdapter. So you can download JS code remotely and run it in the background. that's very non-trivial to do in native land and can be achieved using JXCore. take a look at this sample: https://github.com/capriza/jxcore-android-sample