An update to the Ubuntu 11.04 installer (Ubiquity) finally brings upgrade support to the Ubuntu Live CD. That means that for instance if you use Ubuntu 10.10, when you'll boot the Ubuntu 11.04 Live CD you'll have an option to upgrade (without losing your documents and installed applications). Besides this change, there's also a redesigned partitioner:
(http://lh6.googleusercontent.com/_1QSDkzYY2vc/TWzh8Z786xI/AAAAAAAADNw/8lXqgCMgicY/s500/ubuntu11.04-installer.png)
منبع: http://www.ubuntu-news.net/2011/03/03/ubuntu-live-cd-will-let-you-upgrade-to-newer-ubuntu-versions/