December 8th, 2014: For information on what's new in 1.0, see the official blog post.
The release is available in both the canary channel and the beta channel, so you can check for updates via Help > Check for Update... (on OSX, look in the Android Studio menu). This will download and install a patch rather than download a full IDE image. For all older other versions you will need to install it from scratch by installing one of the below .zip files.
Full installer (bundled SDK) : https://dl.google.com/dl/android/studio/install/1.0.0/android-studio-bundle-135.1629389.exe (813 MB)
Lean installer (no bundled SDK) : https://dl.google.com/dl/android/studio/install/1.0.0/android-studio-ide-135.1629389.exe (250 MB)
Plain .zip file: https://dl.google.com/dl/android/studio/ide-zips/1.0.0/android-studio-ide-135.1629389-windows.zip (235 MB)
DMG: https://dl.google.com/dl/android/studio/install/1.0.0/android-studio-ide-135.1629389.dmg (234 MB)
Plain .zip file: https://dl.google.com/dl/android/studio/ide-zips/1.0.0/android-studio-ide-135.1629389-mac.zip (233 MB)