While the idea of additional control is always a good one, and the addition of programmable macro buttons on a keyboard are welcome, the placement of the "G" keys on the Gaming Keyboard G105
were a bit problematic at first. (G3), (G4), (G5) and (G6) are just to the left of the Tab key, the Caps Lock key, the Left Shift key and the Left Control key, respectively, to the point that I would often either hit the "G" key in addition to the normal key, or instead of actually hitting the intended normal key, since these keys are typically found on the left-most side of the keyboard. This became less of an issue with practice, but it's definitely something to be aware of, as it makes these four normal keys more difficult to hit quickly without looking.
In Call of Duty: Modern Warfare 3, I ended up putting frag grenades on (G1) and melee on (G2)... basically since these were both acceptable last ditch efforts... if I'm about to get capped, I can flail my hand to the upper right hand corner of the keyboard and I might stab at someone, but I'm guaranteed to throw a grenade (well, if I have one - and if I have enough time to finish the action). Things you want to be able to quickly and frequently hit might best be placed on (G3) or (G4), as these are more easily accessible with the left pinky by just reaching over the (Tab) and Caps Lock keys.
The Gaming Keyboard G105 for Call of Duty: Modern Warfare 3 has a lot of good aspects, including the Modern Warfare 3 branding and lighting color scheme, but the placement of the "G" keys keeps coming back to haunt me. I'm just so used to the fact that (Escape), (`), (Tab), (Caps Lock) , (Left Shift) and (Left Ctrl) are the left-most keys on the keyboard, that I often find myself hitting the "G" keys instead of them.
If you're looking to put together a sweet gaming rig for playing MW3 at a LAN party, the G105 for MW3 could definitely help complete your desired look. However, if you find that you have to use that same PC for working on documents later, you might want to have a normal keyboard standing by.