Ubuntu 10.04 Lucid Lynx Alpha 3 has just been released. We already went through most of the visual changes so there's no reason to do that again:
- Ubuntu Lucid Visual Updates: User Icon Added To The Me-Menu, Slightly Redesigned Login Box And More [Screenshots]
- A Few Ubuntu Lucid (10.04) Screenshots
- A Look At Ubuntu Lucid Plymouth Themes [Screenshots And Short Video]
In case you were wondering, no - there's no new theme yet.
Technical details and download: http://www.ubuntu.com/testing/lucid/alpha3