[elithrar]

$ softwareupdate -i -a [install, all] as it avoids the (slow) UI and you can schedule it if you want to.

Not sure if it'll carry across to ML, what with updates going through the Mac App Store there.

[activepeanut]

One downside worth mentioning is that you can't read the full description of each available updates, like you can when you click on an item in the GUI version.

[jasomill]

    softwareupdate -d -a

downloads all updates to /Library/Updates. For each update, you get a .pkg file to install and a metadata file that includes this description.

[_pdeschen]

Indeed. Moreover, I only want to update my jdk when Im ready and have some free time to repair my jdk 1.5 symlinks once the update completes.