I've only had my Android phone (Samsung Captivate) for about 4 months or so and am itching to root and mod it. I'm not 100% convinced I'll get enough out of a rooted phone, but I'm sure if I ever cave in and do it I'll never go back; however, I am a bit worried about getting back to a stock ROM in case I have a hardware issue that requires me to get a warranty replacement. I've read it will void my warranty and that definitely wouldn't be a good thing if I couldn't get it back to stock. I've read about Odin and ROM Manager. It appears that both can get me back to where I need to be if the a problem arose. Lots more reading on XDA-Developers Forums and some extremely convincing reasons why I should root are still required.
UPDATE: Z4root in the Android Market is very simple. Mod'ing on looks really easy with all the other apps out there like ROM Manager, but not to that point yet.