Just finished my first Xbox 360 controller with light up buttons. Did this mod for a friend of mine who more or less wanted a Blanka Themed Controller with Green with Orange trim. So, D-Pad and Thumbsticks are Orange. ABXY, LB, RB, Select, Start and Guide button all light up with LEDs.
I must say it does look rather geekgasmic.
I did have some issues with this due to not having the wiring in the correct place and cutting them in half assembling the controller the first time. So, I ran new wires. No big deal just added some extra time to the process.