OK, if you saw the last mention of the Beta 2 release of Python 2.6 and 3.0 you might have got this message, but the subject line makes it pretty explicit.
Every time a new release comes out it goes through the alpha, beta and release candidate stages without enough people actually downloading it and making sure their applications run. (Then, surprisingly often, within a month or so of the final release someone comes along and says "Hey, this breaks feature "X").
The developers are taking a lot of care to try and ensure that the next version comes out bug-free. Wouldn't it be nice if we could provide an army of savvy testers to saturate the betas with potential problems, so they don't become problems in the release candidates or final release?
Your language needs you! Seriously ... and particularly if you run the Windows version!