This page is a gallery of Logitech keyboards. See also: Microsoft Keyboards Gallery.
This is Logitech's entry level keyboard.
Notice that Logitech uses these symbols for the arrow keys: ◀ ▶ ▲ ▼. However, the up/down triangles are also used for ⇞ Page △/⇟ Page ▽ keys. I see inconsistency.
This one is beautiful! On Amazon, the product name has “Dark Fleur”. The word “fleur” means flower in French. Apparently, this is part of a series of Logitech's “Fantasy Collection”. There's a matching mouse.
This is one rectilinear flatness. Notice, instead of multimedia buttons and app launch buttons, now they are merged into the function keys. So, now to play your music, instead of pressing one button, now you have to press 2 buttons: 【Fn+F11】.
Logitech created a solar powered keyboard. New in 2011.
No more hassle with batteries. Really love it, but not for me, because: ① Not ergonomic. ② Lack of extra buttons.
Getting fancy. But for a pro typist, this is a quicker road to RSI than the $10 ones.
I think all these are bad. You better off with Logitech Gaming Keyboards.