Going back to the Ubuntu root/sudo issue, for most people it doesn't really matter that much. You're still protected by a password. It's just something to bear in mind: when you're new to Linux you hear talk of root, and a newbie working on Ubuntu simply needs to understand that root doesn't apply to them (unless of course you activate it). With most distributions, when you install you have to specify your user and your root password; with Ubuntu you only have one password. My own opinion on this is that root does help to protect your computer. On my computer, for instance, only myself and my wife know the user password, which means the kids can't start the computer by themselves; but only I know the root password. It's not that I don't trust my wife - of course I do! But as she has very limited knowledge of Linux, I know that she can't accidently do anything that would damage the system. As for external threats, I think you're just as well protected by sudo as by root.

If you're on a slow connection you might even want to get the LTS (long term support) version of Ubuntu which is currently Dapper-Drake. It has been around for over a year, and will need less updates. 7.10, even when it comes out next week will want to install hundreds of Mb's in updates during the first couple of months. You will have more issues with it, and for most of those you will have to google and download updates and patches.
If you buy a book about Ubuntu it will very likely include Dapper and Feisty DVD's.