root via the
chainfire method. After doing so you will then enjoy:
1. CWM recovery. allows you to boot up in recovery mode (VOL-DOWN+HOME+POWER) where you can make full backups of your system, restore, wipe setting etc etc etc.
2. opens up a whole new array of useful apps in the market
3. allows you to install custom roms (ie enhanced/modified versions of the firmware)
4. you can freeze unwanted apps (eg. via titanium backup pro)
For me, CWM recovery mode is a MUST for people who like to dabble with various roms, as it allows you to go back to the instant you made a backup, so if you mess something up, then you dont have any worries
As with any download to your device, it can go wrong (eg, your computer could crash, power cut etc), but the chances are minimal. Just ensure you follow the instructions to the letter, have a good level of battery on the device, and I always do an odin download on my laptop, which of course also has battery supply, thus eliminating the danger of a power cut.
Only downside to rooting (or indeed any unofficial firmware update) is it will avoid your warranty, but as long as the divice is not bricked and you can still get into download mode, then you should be able get it back to an official state.
If you want to unroot (the only reason i can think of why you would want to do this is if your sending your handset back and want to put original on) then just download an official carrier branded firmware, and you will be unrooted.