Logitech is very well known for their incredibly high quality and innovative computer peripherals, and their G series is no different. The G15 v1, Logitech's premier Macro keyboard, was larger than average due to it's large assortment of Macro keys (18 keys, with 3 different sets, total 54 macro keys)
This setup tended to anger some individuals and delight others. It's unusually large size made it a bane for anyone with a standard sized desk setup with roll-out keyboard tray. To remedy this situation, Logitech cut off 12 of their buttons, but kept the 3 macro sets, now giving the user 18 macro keys. Although this angers some of the more hard-core Macro enthusiasts, it made the keyboard easily used by people with all different keyboard setups.
Now for the non-tech savvy, you might need the idea of a "macro key, " one of the selling features of this keyboard, explained. In simple terms, the macro keys are programmable buttons that can execute complex tasks of key presses with 1 input. For instance, I could create a macro key, designated on the side, and labeled G1-G6, to actually simulate the pressing of the buttons... ABC, for instance. Now, when I use that macro key, it will press A, B, then C for me.
So with that explanation out of the way, how useful are these keys, and what are they commonly used for? Well, Logitech tends to tailor their items more towards the crowd of videogamers, so an obvious answer would be people who enjoy videogames that require multiple key presses to complete and action (perhaps, switching a weapon, or doing a special jumping maneuver.) So for the casual gamer, playing Bejeweled or a similar game, the keys would be fairly useless in that aspect.
But we can also consider the aspect of use with daily computer use. When complex tasks, perhaps a series of key presses needing to be simulated multiple times to complete a renaming job, the keyboard is perfect.
It contains extensive software for complex macros, and a quick "MacroRecord" key on the keyboard itself for on-the-fly programming.
A quick rundown of the keyboard pros and cons would be thus
Key paint does not seem to wear out, was a problem on the G15 V1, or so I've heard.
Back-lit keys, although non-changeable color (Always orange) Slight dimming options.
LCD screen to display basic information, and extensive information for videogamers. Also has m any plugins, Logitech made and also contributed by the users of the keyboard.
Macrokeys, with QuickMacro programming.
Good key response, groove buttons.
Media keys for quick music and volume access.
Gamelock key toggles "Windows" button, so you don't accidently minimize out of your games after accidently pressing the Windows button (A common problem, as it's very close to key "gaming buttons" such as ctrl and alt)
The screen sometimes (very rarely, not sure if it's by my own fault) does not display any information, or displays useless, unchanging information.
Still fairly large, although not nearly as gigantic as the G15 V1.