20100924 is out now, with a collection of improvements. It's still not much more usable for editing tasks - I'm focusing of fleshing out the structure first. It should start to get more useful once the Python API is enabled (many editing commands, including ctrl+backspace and ctrl+delete rely on this), which I'm currently expecting to happen after projects and session support, which are the next targets.
There's a quick panel in this version, which can be used to switch between open buffers. It works differently to the one in Sublime Text: where as Sublime Text will filter items, X will both filter and reorder them. This makes it much nicer to work with on large projects, which you'll get to see when projects are exposed in the near future. The quick panel itself is still a work in progress - most of the time so far has been spent ensuring that it's fast on large projects (i.e., 50k+ files), and that the ranking gives high quality results.
As an aside, I'm quite happy with the side bar and view resizing in this version - it has detents to help stop the resize at a nice spot (as long as you're not moving the mouse quickly), and the resize areas can be double clicked to resize them directly to the detent.