According to ubuntu 10.04 schedule, it was released yesterday, but Steve Langasek announced that it will be delayed one more day to Friday March 19 ,
Dear developers, Owing to some late image rebuilds for a couple of critical issues that we didn't want to leave our beta users subjected to, validation of 10.04 Beta 1 is still in progress. This means that Beta 1 will not be released on Thursday, March 18 as planned; it will be released tomorrow, March 19. To help us release the beta with confidence tomorrow, please consider participating in the ISO testing today, as described at <https://wiki.ubuntu.com/Testing/ISO>. Also, as you're going through ISO tests, please also help us fill in the blanks on <https://wiki.ubuntu.com/Testing/Plymouth> so we can complete our understanding of the remaining boot-time issues affecting Beta 1 and make Beta 2 truly spectacular! Thanks, -- Steve Langasek On behalf of the Ubuntu release team
Fixed a lot of bugs since alpha 3 version, improved nvidia graphics driver, ubuntu one syncing, new themes, we reviewed in ubuntu fresh look.
Will review it as soon I done download it.
also you can Download ubuntu 10.04 beta 1 from here
And more information, mirrors Here