Over the past year or so I have bought and tested several keyboards; mechanical, membrane and otherwise; and I can confidently say that this one is by far my favourite.The most important feature for me was (and is) the design of the keys and switches. The feel is like no other keyboard that I've tried, with incredibly satisfying key presses. I personally love how the keyboard looks with its thin form and flat, elevated keys. As far as I'm aware, this keyboard is one of a kind in these respects, as these particular switches are a relatively recent innovation.The volume control, USB passthrough port and G keys were complete bonuses. I was worried that it would all be a bit too much; the keyboard too large; but my concerns immediately faded once I had set it up. The volume roller and associated keys are not only incredibly convenient, but also bring an elegant asymmetry to the table, fitting neatly above the numpad. The passthrough allows me to connect my mouse to the keyboard, making the cables that go to the computer slightly more stationary. I have yet to fully customize the G keys, but I enjoy having that option available.Some people have expressed dislike over how the secondary keys, in the number row and elsewhere, don't light up. I personally feel that this is a perk rather than a bug - it makes the rows of the keyboard look rather more uniform, with "one" light per key (technically more for the F keys and so on, but the lights are all at the same height). It does mean that it is difficult to search for them in darkness, but I believe that with minimal effort that can be mitigated: Even if you don't use touch typing, it shouldn't take too long to memorize which primary key corresponds to which secondary key - after that, you can simply search for that key.The keyboard is quite expensive. For me, it is absolutely worth the cost. It looks and feels like it is worth every single penny - Logitech truly spared no expense with both the revolutionary new key designs and mechanisms, and all the extra functionalities. I cannot emphasize enough how much I like this keyboard - typing with it is so much fun that I can barely sit still watching a video; I just want to press the keys!