I like rooting cause you get to theme, I love theming it for fun. Also get to do things that other phones can't do, um you can use a way better rom than the one you have. My Stock Rom was horrible. If I played a game, my battery would be gone in no time. Other Roms here help out with problems like that and you can go from 1.5 to 2.1 which is nice. I also love things people give out here, for example: I recently tried out a keyboard app which had almost every feature and I could basically customize it to my liking. You just have to root, and use your phone and learn it to really enjoy what it is. I have yet to make a rom! Just don't be like the ppl who come here, beg and ask how to root the damn phone, and just install a rom. That's no fun lol.
I also wouldn't upgrade from Vodafone or any carrier. Here where I am, Rogers totally locked ours out. You may end up with a locked SPL or soemthing, you can most likely get the same thing here or better thanks to the devs.