Apple released Mac OS X build 11A419 to developers. Developers, need to install an update from Software Update first - restart - go to the Dev Center and get a redeem code - then go to the Mac App Store, redeem and download (3.7GB).
You'll note that the build number has jumped pretty dramatically: from 11A390 for the initial build to 11A419. This's the build that Apple is considering to be a "GM1" revision internally. And yes, it's said to be much more stable and complete than the previous build.
Having said that, it's unlikely that this will be the actual "Golden Master" copy. Apple may attempt to launch Lion at WWDC 2011, but more likely it's the release candidates that'll be handed out to developers there. A public launch would come shortly thereafter.
Apple has also released Xcode to 4.1 Developer Preview 2: