I think you're looking at this issue from a wrong angle. G13 is not actually better than a standart keyboard. If you've got no problems controlling your character via standart peripherals, you don't need custom ones.
G13 is great for certain people that find it difficult to play on a standart keyboard where you've got WASD for movement and surrounding keys for abilities. I, for example, don't have a lot of experience of such playstyle, and I find it uncomfortable. I don't imply that playing on a standart keyboard sucks; it sucks for me specifically.
As have been mentioned in this thread before, the strong point of G13 (and of a similar device Razer has) is a thumbstick. You don't have to carefully position your abilities around WASD, you just place them however you want and it won't interfere with your movement.
To sum it up, G13 is a great solution for clickers who don't want to learn playing a gosh darn piano (I didn't actually write "gosh", forum filter did). For veteran keybinders, however, it's pretty much useless.