here are my summary for reasons/benefits for rooting my HTC ONE X
1. better battery/phone performance on the custom firmwares - eg, ARHD - efficient and clean
2. Titanium backup
this is by far the most powerful/simple/efficient backup available for android. Many ppl rooted their phone just for this
3. battery meter mods - show percentage of your current battery power on the top bar battery icon.
i dont know why htc/android didnt inbuild this feature..
4. 3 dot menu bar removal mod
background: ICS4 (the base operating system our One X is on) apparently by default has a 'bottom bar' where you can press for menu/option for apps. eg go to evernote or facebook, your notice the bar is right at the bottom of the screen with 3 vertical dots in the middle.
The thing is once you familarise with your phone you'll realise this is rather annoy as it take up that extra space of your beautiful screen.
By rooting you'll be able to apply this mod and get rid of this black bar on the bottom!!! (author re-maps this function to 'long press the home button' which is brilliant).
5. remove branding and bloatware
my came with vodafone branding and useless bloatware for me.
Hope this helps ppl with understanding their phone more