I originally come from an Apple II background (programming in both Apple Basic and Apple Pascal), and then transitioned to both the Mac and Unix when I went to college. Thus I'm very comfortable (in some ways more comfortable) with the command line rather than the GUI, and I'm very comfortable hacking around in the system files.
I admin two Mac OS X system. When I got the first system, I went right away and enabled the root account. I, like a lot of people, thought I would be missing something if I couldn't log in as root.
However, as I used the system, I found that I rarely was using the root account. In general, it was easier to just use sudo. So when I got my second system (my new TiBook which is my primary system), I decided to NOT enable the root account and instead to see if I really missed it.
That was back in November, and as of this day, I have not found any need to enable the root account, and I'm glad that I haven't. I've done things like enable sendmail and other system hacking, and I've found that I don't need an explicit root account. Only on one or two occassions did I need to move something in /System did I run into a problem. However, there's always Pseudo which will launch a GUI app with admin privledges, and there's always the terminal (my favorite).
The reason that I'm glad that I don't have a root account is that I travel and often take advantage of broadband internet services in hotels. In those situations, my system is effectively right on a public network with nothing guarding my system except the software on it. Without that root account, I've cut off 99% of the ways people can hack into a Unix system. Everyone should remember that Unix isn't perfect, and there are ways around the built-in firewall if the attacker is dillegent.
I will admit that if you're not comfortable with the terminal, but you are an experienced Mac user, you may run into situations where you need to modify something with /System. And for many users, there really is no security risk. For example, if your system is only ever connected to the internet through dial-up, the chances of you getting hacked are about the chance of snow in hell.
So the moral of this story is don't enable root unless you have no other choice. It's not me that I worry about, it's everyone else.