At the moment, there is still no public release of Impala. There have been no announcements on any popular web sites, to the Spring mailing lists or forums, or to any other public forum. This is deliberate. This is not because the necessary features are not present. Most of the functionality needed for a public release is present, and the code is usable and good quality. There is is enough functionality to provide real benefit to a project using Impala.
What still remains is to be absolutely sure that the Impala internal interfaces are correct. For the last few months (yes, literally!), I have been doing extensive refactoring, with the result that I am progressing towards this point. If users come up with a whole new set of requirements and ideas on how it can be used, there should be a clearly defined set of interfaces to build upon.
The first public release of Impala won't be just before going 1.0. However, it will only occur when I have reached the point that I am satisfied that the interfaces are as correct as I can make them, to support extensibility and maintainability moving forward. I think I am quite close. The interfaces are in pretty good working order, and the organisation of the code seems to make good sense.
I need to spend a bit more time working on the interactive test runner, and on deployment issues. Most of the work I've been doing with Impala has been within Eclipse itself. And of course, samples and documentation, although the first public release doesn't need to depend on these.