Since you have an unlimited data plan, free tethering is the main benefit for me. Ability to use your phone as a hotspot for tablet, laptop, etc. You can bring a tv and xbox to a tailgate and play xbox live if you wanted. No need for a data plan for your tablet. Use your laptop to surf while on a long distance trip. Wifi hotspot for your laptop while in an airport/hotel without wifi. Dont need to pay for wifi while in vegas. Power goes out at your house? Still have wifi.
Next best thing is removing all the bloatware that slows down your phone and drains your battery. Download titanium backup, freeze all the apps that you never use but run in the background.
Also when you get more in depth flashing new roms to completely customize your phone homescreen/lock screen/app drawers/launchers.
Go here to get started, read a ton before you do anything major.
http://forum.xda-developers.com And take everything I say with a grain of salt because I am definitely a novice.