I am looking forward to Slingshot having free off peak and carrying data over month to month, and want to know if I can have Software Update run when I want it to, like after 1am?

Which version of OS X are you running? 

In any case, you can go the Software Update panel in System Preferences, and tell it to check for updates daily, weekly, or monthly, which it will do at the same time of the day for any of the periods selected as long as it isn't asleep.  Hence you can do the first run during the off peak period, and select the box "Download important updates in the background", and when you come back in the morning the updates will be ready to install. 

Another option is to use a download manager to download the updates from Apple's site on a scheduled basis.  For me, I'd probably use the former method, as apart from having to stay up once, it uses only Apple's built in functionality.  Remember that you will have to ensure your machine doesn't sleep, as then the routine won't run until morning.

I'm using 104 at the moment but looking to move to 10.5 soon with my new MacBook

Sounds pretty straightforward - run it one Sat or Sun morning when I'm coming home from a night out on the town

Well you are being creative tonight, aren't you?

I guess that could work, yes.  Or you could just run it every weekend when you crawl towards home after attempting to kill your liver.

Is the size of the updates an issue?  This is something I never considered with regard to OS X.

I'm not sure I'd be in any state to do anything when I get home from a night out.  Don't think I should be let near a computer in that state!

There are a couple of different types of updates for OS X.  The first is a 'delta' updater that takes the OS from a previous point release to the current.  e.g. 10.5.1 --> 10.5.2.  These are smaller as less data is required for this type of update.  The 'combo' updater is for more than one step, e.g. 10.4.x --> 10.4.11.  These are larger as more file changes are required. 

If you use Software Update regularly the chances are you are up to date, and delta updates are used.  These are anywhere from 30MB-150MB.  If you manually update, or are more than 1 update behind, a combo will be applied, which are anywhere from 80MB - 300MB (although there was one once that weighed in at 458MB!). 

So in summary, they are of reasonable size, but generally come once every 2-3 months, so aren't that often.

Excellent.  Thank you for the considered reply.  It appears that size of the software updates is more than manageable given Slingshot's generous broadband plans.

Karl - thanks for this.  I'm sure you can help me if I have any problems right?

wish i could afford apple products

Me too

You have an Apple computer!  Also an iPod, too.  Are you becoming delirious?

No, but I want a NEW Apple computer, and a NEW iPod!  I can't afford all the Apple gear I would like