Java 6 has been released (both Wildfire and Spark are built using Java). Normally, the fact that we use Java isn't relevant unless you're building plugins or making customizations to the code. However, the Java 6 release merits a mention for several reasons:
This is the first Open Source release of Java. That means that in the near future, you'll see Java 6 ship with many Linux distros. That will make it even easier to get Spark and Wildfire running on Linux.
Java 6 support for epoll on Linux fits in nicely with the scalability work we're doing for the next release of Wildfire. Linux users will be able to scale Wildfire to many tens of thousands of connections.
There are big improvements to Swing (the user interface library) in Java 6. That means Spark will be faster and prettier with things like font anti-aliasing, much faster re-draws, and quicker startup time.
You can install Java 6 now, or get it automatically bundled with the next releases of Wildfire and Spark.