For now the Bazaar repositories for most of the Ubuntu source packages are being housed at package-import.ubuntu.com, but with time they will be integrating these services with Launchpad and will be introducing several new features. The announcement regarding this major transition was made this morning on ubuntu-devel-announce.
Aside from this developmental change, there are several exciting features for Ubuntu 9.04 such as improved boot performance, many mobile optimizations and changes, ARM architecture support, improved encryption capabilities, an updated kernel and X Server, and many other changes. Ubuntu 9.04 Alpha 1 was made available last weekend. The final release of Ubuntu 9.04 is planned for the 23rd of April (release schedule).