Note:- This is an alpha release. Do not install it on production machines. The final stable version will be released on April 29, 2010.
Upgrading from Ubuntu 9.10 or Ubuntu 8.04 LTS
To upgrade from Ubuntu 9.10 on a desktop system, press Alt+F2 and type in "update-manager -d" (without the quotes) into the command box. Update Manager should open up and tell you: New distribution release '10.04′ is available. Click Upgrade and follow the on-screen instructions.
To upgrade from Ubuntu 9.10 on a server system: install the update-manager-core package if it is not already installed; edit /etc/update-manager/release-upgrades and set Prompt=normal; launch the upgrade tool with the command sudo do-release-upgrade -d; and follow the on-screen instructions.
Ubuntu 10.04 (Lucid) alpha 3 included
Ubuntu Lucid Alpha 3 includes the latest GNOME desktop environment with a number of great new features.
Default search engine has been changed to Yahoo! Default Home Page will use either Google or Yahoo! depending on user setting.
Linux kernel 2.6.32
Alpha 3 includes the 2.6.32-14.20 kernel based on 18.104.22.168.
KDE SC 4.4
Alpha 3 of Kubuntu features the new KDE SC 4.4. For more information about new features in Kubuntu, see https://wiki.kubuntu.org/LucidLynx/Alpha3/Kubuntu.
Lucid Alpha 3 sports full removal of the hal package, making Ubuntu faster to boot and faster to resume from suspend.
Major new version of likewise-open
The likewise-open package, which provides Active Directory authentication and server support for Linux, has been updated to version 5.4. The package supports upgrades from both the officially supported versions 4.0 (Ubuntu 8.04 LTS) and 4.1 (Ubuntu 9.10), as well as the likewise-open5 packages from universe.
Since this upgrade involves a lot of configuration file changes and in-place database upgrades, testing and feedback is appreciated.
New default open source driver for nVidia hardware
The Nouveau video driver is now the default for nVidia hardware. This driver provides kernel mode setting, which will give improved resolution detection. This driver provides hardware accelerated 2D functionality, like the -nv driver it replaces. The nouveau driver is being actively developed upstream and we anticipate this will enable faster bug fixes for problems encountered.
Improved support for nVidia proprietary graphics drivers
Three different NVIDIA proprietary drivers are currently available: nvidia-current (190.53), nvidia-173, and nvidia-96. Thanks to a new alternatives system, it is now possible to install all three of these packages at the same time (although it is only possible to have one configured for use at a time).
Social By Default
We now feature built in integration with Twitter, identi.ca, Facebook, and other social networks with the MeMenu in the panel, which is built upon the Gwibber project, which has a completely new, more reliable backend built on top of desktopcouch. Gwibber now also supports a multi-column view for monitoring multiple feeds simultaneously.
New features for Ubuntu Enterprise Cloud (UEC)
The Ubuntu Enterprise Cloud installer has been vastly improved in order to support alternative installation topologies. UEC components are now automatically discovered and registered, including for complex topologies. Finally, UEC is now powered by Eucalyptus 1.6.2 codebase.
Download Alpha 3
Get it while it's hot. ISOs and torrents are available at:
http://cdimage.ubuntu.com/releases/lucid/alpha-3/ (Ubuntu Desktop and Server)
http://uec-images.ubuntu.com/releases/lucid/alpha-3/ (Ubuntu Server for UEC and EC2)
http://cdimage.ubuntu.com/kubuntu/releases/lucid/alpha-3/ (Kubuntu Desktop and Netbook Remix)
http://cdimage.ubuntu.com/ubuntustudio/releases/lucid/alpha-3/ (Ubuntu Studio)
Check more details from here