Sublime Text X 20101230 is out now. There are several polish related features, but the headlining feature is the new project support.
Projects in Sublime Text X work differently to those in 1.x: In 1.x, projects are a set of directories, while in X, they're a mini-session, containing a set of directories, open buffers, changes to those buffers, and other transient settings. Switching between projects is instantaneous: any unsaved changes to files will be recorded in the project, and then the new project is switched in. This makes switching between tasks quite efficient.
It's also possible to work with ad-hoc projects (i.e., with no .sublime-project file) by simply dragging folders onto the side bar.
There are still several more things to implement for proper project support, the most significant of which is excluding unwanted files from projects.
Being able to switch between sessions was a frequently requested feature for Sublime Text 1.x, and I'm keen to hear how everyone finds this implementation.
Also, I'm aware there are many people who would like to try out Sublime Text X, but aren't able to because they haven't yet purchased a license for Sublime Text. I'm hoping it won't be too long until there's a public alpha available.