Ergonomics, the keys are very comfortable, not too slippery but not too rough either the touch. They are slightly quieter (except perhaps the space bar which is very slightly "noisy") to me than my netbook, while being larger and therefore more easily accessible. Typing is fluid. The palm rest is quite comfortable in a "rubber" type of material of good quality.
Side design, this keyboard is really, really a success. Logitech did not opt for the questionable mode "while glossy" and chose a matte material, very good quality, rather rough but pleasant to the touch. The transparent tape around the keyboard is successful, it frames the keyboard nicely but discreetly. The selected font is nice and letters are finely engraved. The backlighting is really nice and helpful, it does not dazzle and knows how to combine design and functionality (all 3 levels of lighting are more practical).
The finish is excellent, I have not no "slack" in the key mechanism, and the keyboard is surprisingly heavy (relatively, of course), guaranteeing a certain solidity.
In summary, this keyboard is excellent for the most demanding programmers, for those who frequently use a word processor or simply for those who want to beautify their office with a beautiful and functional keyboard. I fear though he did not really please the hardcore gamers, who complain of a lack of certainly find shortcuts and the buttons are too soft for the game.
A good investment if you can shell out 68 for this keyboard, please!