As an awful lot of points have been covered here by other users, I'd like to cover this product from a different angle. Firstly you would need to be a typist to fully appreciate the finer aspects of this keyboard. If you're a hunt and peck, then I don't think you would get the most out of it and would possibly be better served with something cheaper.
The illumination is a bit like a Xerox machine. You don't really know you need it until you've tried it. Once you've used it and have got used to it, there's no going back, and you begin to wonder how on earth you managed without it in the first place.
The keys have got the perfect weighting and just the right amount of travel and all in all is absolutely perfect and a joy to use. The function keys offer a different way of working, but like all things new you need to give yourself time to adjust. Once you've used it for a while, you soon settle in. Also, the keyboard itself is nicely weighted and sits positively on the desk and doesn't slide around when you get a wiggle on, as my old Microsoft one used to.
Like every other keyboard, underneath on the front edge there are little legs that you fold down in order to tilt the keyboard towards the user. When mine first arrived naturally the first thing I did after unpacking it was to fold down the little legs and place it in front of me. There it sat tilted towards me, as you would expect, looking resplendent. Then I began to wonder. It occurred to me just how weedy the little legs were. They couldn't be described as flimsy, as Logitech would have more sense than putting flimsy legs on such a premium product, but they are indeed.......weedy. Very weedy indeed. So I lifted it up and turned it over and looked at the weedy legs for some time. Then the thought crossed my mind, that Logitech in their wisdom didn't really want me to use them. It was as if Logitech had installed the weedy legs as an afterthought but didn't really want you to use them at all. After all, if the legs were intended to be used properly and weight to be put upon them they would have made them a lot more sturdier than they are. So for the first time in my life I decided not to use them at all and to leave them folded up out of the way, where they are presumably intended to stay.
That was the beginning of a miracle. With the keyboard lying flat, the user has no choice but to sit up and take notice of what he or she is supposed to be doing. I've found my whole posture has improved immensely. My back is straight and my arms and hands in a more natural position which is absolutely ideal for a long day's typing. Slouching over a keyboard with head drooped is now a thing of the past, and my productivity has certainly improved and increased no-end. Logitech have certainly thought this through and as far as I'm concerned, it's a stroke of genius. Well done Logitech. I shall certainly be taking a keen interest in Logitech and their products in future as they seem to have left Microsoft far behind. Come on Microsoft wake up, you're asleep again.