I mean anyone can always "choose" not to upgrade but then you'd feel a bit left along since others boasting about how cool their new OS version looks, etc which is very tempting ;-). So I don't know about ya all but even though sometimes I totally don't need but I find myself forcing to install the latest Ubuntu release as soon as it hits the downloads.
On the other hand if you run Ubuntu on a Server or even on a desktop where you'd love to have a more stable, secure environment then rather than installing/upgrading the whole OS every 6 months which is a irritating + may make your previously secure network a bit buggy (if the "new versions" did have few bugs, etc) then luckily Ubuntu Linux has a dedicated release/version that's known as LTS or Long Term Support.
The LTS version do under go a lot of testing for stability and security before releasing thus you may not see the most newest version of the packages available as with the 6-months cycle release edition. But since the aim is to enhance the stability and the security, this is understandable.
Anyhow the latest news is that the Ubuntu LTS team has just released the 10.04.3 version. This as usual brings a lot of bug fixes to the Kernel and to individual applications rather than features. Few GRUB related and Ubiquity related bugs, a huge list of Kernel bug fixes and individuals applications such as Brasero/Firefox/Compiz/GDM, etc are also listed in this official 10.04.3 LTS release log page. In addition to that, the official Ubuntu 10.04 LTS LiveCD is also updated with the above bug-fixed packages. So from now on whenever you download the 10.04 LTS version you'll be getting the 10.04.3.