For business use, the largest driver of Linux adoption has been the Enterprise Linux releases.  Product names aside, I am referring to those Linux-based distributions that offer longer, multi-year support commitments for a version of the product.  To date, the primary examples of this (and not coincidentally market leaders) have been Red Hat Enterprise Linux, Novell SuSE Linux Enterprise Server and Mandriva Linux.

Matt Zimmerman of the Ubuntu team has just announced that:

Ubuntu, Kubuntu and Edubuntu 6.06 LTS will be the first Ubuntu releases with long-term support: three years on the desktop, and five years on the server.

I haven't installed it to check it out yet, but I probably will once it is released.

Ubuntu, like the other Enterprise Linux vendors, has its share of security vulnerabilities, which can be viewed at http://www.ubuntu.com/usn.  I've not analyzed these in the past given the short lifecycle, but now that they offer a more enterprise-length lifecycle, I may start.  It'll be interesting to compare their first year with Windows Server 2003 and with the first year of Red Hat Enterprise Linux 4, as reported in Red Hat RHEL4 Risk Report.