Updating all your Macs with MacOS X Server - For all you techy guys out there (if you know this already, ignore), there is a way to download system updates only once then feed the updates round your network, via the Server's Software Update Service feature, without using up loads of valuable internet bandwith and downtime.
Or do it manually, either with Apple's Remote Desktop program, or by applying the updates on each Mac yourself, once you've downloaded the files; practical, if you only have a handful to update. The point being, is that you don't need to use the Software Update feature on each and every Mac, to do the updates - one, it's a bind to do, and second you have to restart each Mac for every Security Update and System Update going. Apple has an IT-Pro web page, if you require more advanced info.

Important Notes
A combo update (combo = combined update) updates any previous version of OS X 10.4 to that current version. This does not mean that you can update MacOS X 10.3.x to 10.4.x with the 10.4.7 combo update, you need to buy MacOS X 10.5 if you want the latest OS X. An incremental update updates the OS from the last incremental version, for example, from 10.4.6 to 10.4.7. A Delta update is explained here - it is an smart update, which aims to reduce the filesize of the update, and works only with Software Update.
Remember: All major MacOS X releases 10.1, 10.2, 10.3 & 10.4, cannot be updated with free system updates, eg. 10.4.1 update will not upgrade any previous major version of MacOS X, you will have to buy the latest version of OS X first.