Ubuntu 9.04 Beta includes the 2.6.28-11.37 kernel based on 126.96.36.199.
Ext4 filesystem support
Ubuntu 9.04 Beta supports the option of installing the new ext4 file system. ext3 will remain the default filesystem for Jaunty, and we will consider ext4 as the default for the next release based on user feedback. There has been extensive discussion about the reliability of applications running on ext4 in the face of sudden system outages. Applications that use the conventional approach of writing data to a temporary file and renaming it to its final location will have their reliability expectations met in Ubuntu 9.04 beta; further discussion is ongoing in the kernel community.
Ext4 support in GRUB was provided by Colin King. If you choose to upgrade your / or /boot filesystem in place from ext2 or ext3 to ext4 (as documented on the ext4 wiki), then you must also use the grub-install command after upgrading to Ubuntu 9.04 Beta to reinstall your boot loader. If you do not do this, then the version of GRUB installed in your boot sector will not be able to read the kernel from the ext4 filesystem and your system will fail to boot.
Ext4 support in gparted has been provided by Curtis Gedak.
Ubuntu 9.04 Server Edition makes it easy to experiment with cloud computing. Eucalyptus, an open source technology which is included in Ubuntu as a technology preview, enables you to use your own servers to deploy, experiment and test your own private cloud that matches the Amazon EC2 API. You can dynamically create virtual machines, configure multiple clusters into a single Cloud and even provide an EBS (elastic block storage) equivalent and an S3 compatible storage manager.
Turn-key mail servers
The dovecot-postfix package in Ubuntu 9.04 Beta provides an easy-to-deploy mail server stack, with support for SMTP, POP3, and IMAP with TLS and SASL.