Upgrading WPMU to WPv3.3

Hi, I have recently set up an WPMU site, hosting with psek. (they were great and actually set up the site.) I currently run 3.0, notice I need to run 3.3 to use the latest version of marketpress. I figured i'm best off to be running the latest from the start.

so...

I have backed up the whole database from Control Panel.

Does the Automatic Update from the dashboard work reliably on MU sites, or is there a better way to handle it.

I don't want to create a tech headache doing a simple updgrade.

Thanks in advance.

Mark