I first encountered Ubuntu while going to school for a linux certification. I was fairly accustomed to how things were done with rpm packages and how things worked in opensuse. This particular lab I was studying told me I should be using Ubuntu. At the time, the distribution supplied to install and use was Hoary Hedgehog. I quickly realized I hadn't supplied a root password during install, and the lab manual mentioned nothing about it. So, of course I googled it to find out why. I found out Ubuntu implements sudo to give users access to root commands. Interesting. I thought I could deal with that. But, after continuously entering sudo in front of any command that needed root access, it got very old. I thought there must be a way to enable the root account. It turns out, it's actually very simple to do just that.
All you need to do is: sudo passwd root
Then it will ask you for your password, then you have to enter root's new password twice and you're all set. Now you can login to the root account just like you would on any other distro.
Some may argue that sudo is a security measure, because it's in a way disabling root's account. This is true to a degree, but you could also argue that now there's only one password to circumvent instead of two. And user passwords would typically be much simpler than a root password, for convenience. Some may think enabling root's account opens another hole, by allowing the user to login to the graphical environment as a root user, since that's what they may be used to doing in other less secure OS's (microsoft, anyone?). This isn't the case with Ubuntu though, as gnome by default does not let you log on as root.
A definite advantage to having sudo by default is that new users can't login to the root account and obliterate the system with a command a buddy jokingly tells them to execute (rm -r / is a fun example). But any experienced user would have no issues using root's account, as that's what they're accustomed to with other distros anyway. Personally, every system I install Ubuntu on that I'll be using gets a root password assigned. I couldn't have it any other way.