I like how you only have to highlight something to cast a skill on it.

Up/down for party members, left/right for monsters. If a person in the last party slot needs healing, you can just press up two times, heal, and you never lose your current target.
On the keyboard you'd have to press F8, cast, then F2 again (back to tank) just to heal a person. The physical distance between F8 and F1 is huge.
Also, between the CTRL/ALT keys and the numbers, there's a lot of space. Using Alt + 7 for example is quite a chore. While on controller there's no physical distance to travel. You have 16 skills under your thumbs. 16 more in a mere R1 press.

Personally, I've never got used to playing on a Keyboard. Even with one and half years of WoW, I adapted to FFXIV's controller scheme and I think it's almost perfect.