We've never really tested keyboards before now at THG, because most of them were more or less the same where feel and ergonomics are concerned. As for layout, the choice between traditional or the ergonomic design pioneered by Microsoft is a matter of personal choice. This meant looks and shortcut keys were about all that differentiated keyboards. (Of course I'm referring here to standard keyboards, not ones designed for a specific use, such as gaming.)
With its LX keyboards, however, Logitech has introduced a real change that's worthy of attention. First of all, the keyboard has become perfectly flat. There are no curves on either axis, and all the keys are the same size and have the same travel, spacing, and depth. Only the lower keys are slightly rounded for better touch. If you don't like typing flat, there are two feet you can deploy to get a slight overall inclination.
I was skeptical of this at first, since I prefer curved, tilted keyboards. But my professional integrity as a tester won out and I decided to start using this keyboard myself. I've now been using it for a month (including while writing this article.) And I have to admit that in use, this arrangement is more relaxing and causes less confusion among the keys.
In passing, let me say that for gaming, and for FPS games in particular, these keyboards are very well designed. The arrow keys are wide, slightly curved, and provide a particularly restful position for the palm. Fans of FarCry and Doom 3, give it a try!
The second noticeable change is that the feel of the keyboard has been completely re-engineered. The keys no longer depress suddenly with a stop and sound that provide feedback. Instead, the key's travel is soft and cushioned. The moment the keypress "registers" is felt as an increased firmness, but not as a stop. I was immediately won over by the feel; it's more pleasant and more precise. But, not trusting my own enthusiasm alone in judging this new keyboard's ergonomics, I equipped some of our editorial staff with the unit. The opinion was unanimous: they all want this keyboard!
A pleasant side effect of the new layout and mechanics of the keys is that the keyboards are very thin - only a few millimeters thick. This is a plus in terms of desktop space use and design.