I have the G11, because I wanted 18 keys not just 6, and I am completely opposite from you: all I ever use is the G keys now.

My index, middle, and ring fingers rest on G9, G8, and G7 respectively when at rest, with my thumb position for easy access to CTRL and ALT. My pinky hovers off the side of the keyboard. This way, with just the six middle keys I am able to access 18 different spells, abilities, macros, or actions easily and quickly. I move using the mouse or the arrow keys. (I also have the G5 mouse, thumb buttons FTW)

I use the topmost row for buffs, the second row for not-so-common spells like WotF, Banish, Enslave Demon, Spell Lock, Seduction.

I don't use SHIFT w/ my thumb because it's too awkward, and besides my G keys on the M1 set are programed to SHIFT+F1 through SHIFT+F12 for G1 through G12, then CTRL+F1 through CTRL+F6 for G13 through G18. I used CTRL for the lower set because it's very awkward to try and thumb CTRL while using the lower buttons, so I had no need for CTRL as an additional modifier down there.

Definately worth trying, although if you're the type that calls spells w/ your right hand (my friend uses the numpad) and uses the WASD keys for movement, the switch-off might be difficult to adjust to.

To give you an idea: G7 is Incinerate, G8 is Immolate, G9 is my primary curse (linked to my action bar so I can switch it around). CTRL+G7 is Conflagrate. CTRL+G8 is Fear. CTRL+G9 is my secondary curse (again linked to my action bar so I can switch it when needed). G10 is Lifetap, G11 is Drain Life, G12 is Drain Soul. SHIFT+G10 is Shadowburn, SHIFT+G11 is Howl of Terror, and SHIFT+G12 is Death Coil. And then it gets even more fun because ALT+G7 is Rain of Fire, ALT+G8 is Hellfire, and ALT+G9 is Seed of Corruption, so I have complete access to all my AoE just by stretching my thumb a bit to ALT. I also have G18 bound to a /stopcasting macro which is useful since Esc and Space are hard to reach w/ this setup.

I totally just wrote a long comment on this, and now it's mysteriously vanished.