Welcome to Oneiric Ocelot Alpha 2, which will in time become Ubuntu 11.10.
Pre-releases of Oneiric Ocelot are *not* encouraged for anyone needing a stable system or anyone who is not comfortable running into occasional, even frequent breakage. They are, however, recommended for Ubuntu developers and those who want to help in testing, reporting, and fixing bugs.
Alpha 2 is the second in a series of milestone images that will be released throughout the Oneiric development cycle.
New packages showing up for the first time include:

• Linux Kernel 3.0-rc5
• gcc 4.6.1 compiler
• Firefox 5.0
• Thunderbird 5.0
• A Mesa 7.11 snapshot.

You can download Alpha 2 images here:

• http://cdimage.ubuntu.com/releases/oneiric/alpha-2/ (Ubuntu, Ubuntu Server)

Additional images are also available at:

• http://uec-images.ubuntu.com/releases/oneiric/alpha-2/ (Ubuntu Server Cloud )
• http://cdimage.ubuntu.com/xubuntu/releases/oneiric/alpha-2/ (Xubuntu)
• http://cdimage.ubuntu.com/edubuntu/releases/oneiric/alpha-2/ (Edubuntu)

Alpha 2 includes a number of software updates that are ready for wider testing. This is quite an early set of images, so you should expect some bugs. For a more detailed description of the changes in the Alpha 2 release and the known bugs (which can save you the effort of reporting a duplicate bug, or help you find proven workarounds)


Source : ubuntu-geek