The On/Off switch can be found in the top right corner of the K800.
Such a switch is very useful for a wireless keyboard with backlight because it helps save battery power when the keyboard is not in use. Next to the switch there is a 3-way charge indicator you can enable by pressing Fn+F7. According to Logitech, one battery charge should be enough to power the keyboard for 10 days, which is very little for ordinary wireless keyboards but quite long for a model that has full-featured backlighting of all the keys. The small round hole is a light sensor which is supposed to help adjust the level of backlight depending on ambient lighting but it didn’t do anything even when I covered it with my finger.
The photo above makes it clear that Logitech has given up its nonstandard layout of the editing block in the K800. As opposed to the wired Illuminated Keyboard, the positions of Insert, Delete, Home, End, Page Up and Page Down are standard and compliant with the 101-key enhanced keyboard specification. The Print Screen, Scroll Lock and Pause/Break buttons haven’t suffered any modifications, either. The top row of buttons above the numpad serves to control the volume. They did not work with the M-Audio Audiophile 2496 sound card installed in my computer, though. The rightmost button conveniently launches Calculator but you can redefine it with SetPoint to do something else.
There is nothing unusual in the central part of the keyboard: the Cyrillic version has an L-shaped Enter, a short Backspace and a wide Fn, like in the wired Illuminated Keyboard. The right Win button and the rarely used Context Menu are missing; the latter's function is combined with the Print Screen key. The American version of the K800 has a long and low Enter with a backward slash above. Preferring a specific version is a matter of taste: I personally like the L-shaped Enter with the backward slash to the left of it.
The left part of the keyboard copies the layout of the K800’s wired cousin. We can see a tiny square Shift you may need some time to get used to and a short Tab. This shouldn’t be a big problem because, as I know from my vast experience of text editing, the right Shift is used far more frequently, and the latter key is large in the K800. You can’t miss it with your finger. Still, I don't think it is an optimal solution to shrink the left Shift to the size of an ordinary alphanumeric button and to put a second backward slash next to it. Enlarging the left Shift at the expense of that backward slash would be better. Well, such trifles are actually a matter of personal taste. Some users may find this layout the most optimal one. And even if you don’t, getting used to such minor changes in the shape and position of the keys is a very quick process.
Traditionally for Logitech, the buttons F1 through F12 all have dual functions. The additional function, indicated in orange, is enabled by pressing the button together with Fn. Some of these extra functions are system-wide and cannot be redefined with SetPoint (like Fn+F5/F6 which adjusts the brightness of the backlight). You can normally redefine only the first block of the functional buttons together with F8 and F9.
Overall, the layout of the Logitech Wireless Illuminated Keyboard K800 resembles that of the wired Illuminated Keyboard but the classic layout of the editing block of keys is definitely an advantage of the wireless model.