The latest 6 monthly Ubuntu build, Karmic Koala, was released to the public on Oct, 29th. That is now an option when ordering a new VPS or for a fresh install on an existing VPS (contact us if you have questions about retaining your data after the reinstall).
If you don't want to reinstall an existing server, but you would still like to use the latest release, a simple apt-get dist-upgrade can bring you from Jaunty Jackalope (9.04) directly to Karmic. I'm only aware of 1 issue that has cropped up which, as Liz noted, can be remedied with a simple kernel change.
Ubuntu's 6 monthly build schedule offers a support window of 18 months via the standard Ubuntu repositories. The scheduled end-of-life for Karmic is April, 2011. LTS releases (next one scheduled for April, 2010) bring about longer support windows (5yr for server releases) and I prefer those for production systems. Although given the relative easy of distro upgrades with Debian derivatives, this isn't a major sticking point with me since it's usually pretty painless to move forward 1 release at a time via dist-upgrades. All end-of-life dates can be found on the Ubuntu wiki.
Karmic brings along bug fixes and minor package updates, but I'm not aware of any major changes or package upgrades. If you would like to see what versions of your required software have been packages in the main repositories, you can view those at distrowatch.org.
If you need any help planning a migration to the new release or if you just have some questions about Ubuntu in general contact our support team and we will help.