I have this keyboard and it's actually flawed to the point where I've been trying to sell it for weeks.
The supposed proximity sensors for the backlight are USELESS. You take your hand off the keyboard in the dark, a few seconds later the backlight goes off, then you're supposed to wave your hand around it until it comes back on or press a button.
There is no ALWAYS ON option, there are hundreds of users on Logitech forum who asked for an always on option.
Even for th reduced price, no thanks, flawed backlight implementation and Logitech refuses to acknowledge it.
High quality mice? Is this a joke? Maybe in 2010. Now they are overpriced hunks of plastic with chinese parts that are very likely to produce defects(usually double clicking) within a year since the day of purchase. Customer support is horrible too. Honestly just stay away and buy something else