It's out. jQuery 1.0 was just announced and it's HOT. The rollout is still in progress, as there's a ton of work that involves getting the API and documentation ready, test cases, screencasts, visual docs and supermodels ready.
Use it wisely. If you break it, pay for it. OR log a bug.
There's a LOT of new functionality in the new build so keep a close eye on the documentation as it comes out of the oven and consider joining the discussion list.
So no, it's not just a library, it's a language. Ok, not officially a language, but it might as well be. With it, many people are writing way cool plugins with little code. Exactly what we all need.