I Rooted my phone for one reason only... i was really really really curious about the process. it seams fairly safe as long as you READ EVERYTHING you can get your hands on BEFORE doing it.
usually when people go wrong with modding ANY device its because the didn't prepare for the process
Root benefits that I use:
Teathering (making your phone work like a mobile broadband dongle)
Apps2SD (although i am not sure this is working properly, needs some kind of interface)
De-branding (no more stupid Planet-3 link i cant delete or silly 3 logo on boot up)
SU privileges - Got some cool widgets that do things with reboot that i can hardly fathom, all useful though, and a side effect of super user access.
Mine has only been rooted a few days so i can not really tell you any more but i am sure its only going to get better from here
all that said, it COULD do wrong so if you do it, then make sure you have a better reason that curiosity