I wouldn't recommend it for everybody, as the process can be quite confusing, but I have no regrets doing it. Apps2SD+ is brilliant.
Basically, rooting gives users more control over their phones, and also means installing custom software (ROMs) that developers have "cooked up".
For instance, there are Froyo (Android 2.2) ROMs floating around on the place already, which give our Desires 720p video recording, and of course, the latest Android 2.2 :P
I'm not brave enough to venture into custom 2.2 ROM territory yet though, as there are quite a few bugs that the devs need to iron out :)