Pros: I've been using this keyboard as a HTPC/Gaming PC keyboard for over a year with absolutely zero issues.

The back lighting is fancy, the keys have just the right feel to them (typing anything is a treat), and the battery lasts a very long time! I like the calculator button, and the sleep button (FN + F8) is really convenient for an HTPC setup!

But the best thing about it? The customer service! Since I use this keyboard on the couch, dropping it on the floor is always a potential hazard. Recently, it fell so hard into the corner of my coffee table that a key broke off. I called Logitech to purchase a new key and instead they are sending me a brand new unit! For free! And I don't even have a receipt!!! That right there should negate almost every bad review about this device. I'd give more eggs if I could!

Cons: Uses the same frequency (2.4 GHz) as a lot of other wireless devices such as wireless routers. Not that I've had an issue with the keyboard, but I share the same tiny USB receiver with a Logitech Anywhere MX mouse (also love it) and noticed severe lag issues with the mouse until I changed the channel on my wireless router - now everything is PERFECT. I would assume everyone who says not to use this for gaming or that it's not very responsive is probably only dealing with this very simple problem. So not really a con if you can figure out how to change the channel your router is broadcasting on.

Other Thoughts: I've read a previous review about bad battery life, and that is just not true. I've had this keyboard for almost 2 years and I've had to recharge it somewhere around 10 times. I'm in the habit of switching it off whenever I'm not using it, and that seems to be working really really well.

Pros: Works on glass, dark brown leather, my knee.... pretty much anywhere (hence the name). Battery lasts a long time and has survived many accidental drops. Very nice to have such a small USB receiver. The unifying receiver allows multiple Logitech devices to only utilize one USB port, which I can attest to working flawlessly.

Cons: Works great for gaming, but there are better options if you are sensitive to a few extra milliseconds like bluetooth and wired mice. For using it on the couch or in a hotel or in front of a customer, I love it.

Other Thoughts: After owning two I have not seen some of the issues that other owners are experiencing (double-click issue or power switch not being fully pressed) but I HAVE had a terrible lag issue that was more noticeable when web surfing or playing online games.
It turns out this mouse, as well as many other wireless devices, uses the same 2.4 GHz frequency as my router. By simply changing the channel of my router from 10 to 11, I completely fixed the problem. If you ever hear anyone complaining of 'lag' issues, it means they weren't able to figure this out.