I'm not easily impressed, but I am impressed with this keyboard. Here's what I like specifically:
* Universal: I bought this specifically for my Raspberry Pi 2 running RetroPie 3.0. Not only is it Pi friendly, it also works on my Windows 7 computer, and my Sony Xperia tablet running Android 5.
* Visibility: I didn't think back-lit keys would be valuable, but the fact is you MUST look at thumb keyboards while typing, and without the backlight, it's difficult to see the keys in a darkened room. So this turned out to be a great feature. The backlight can easily be turned off, too, if you want to preserve battery power in bright environments.
* Touch: The keys are advertised as being "soft", which makes be nervous because some soft-key keyboards are so mushy that you can't tell by the feel whether you've actually pressed a button. No so with this keyboard. The keys have a soft finish, but you know when you've pressed a key.
* Comfort: The keyboard is sturdy but weighs almost nothing. It feels very nice in my hands, too.
* Simple alternative to Bluetooth. I have a Bluetooth dongle for my Pi, but configuring BT is not fun, even in Windows. This is a configuration-less solution, even in Linux. It just works.
* Less clutter: Not only is this keyboard compact, it replaces two devices (keyboard and mouse) with a single device that doesn't require a lapdesk or hard surface. Very convenient.
* Full function: It's a full keyboard and handles all key combinations, such as Alt-Fx combos in Linux.
What do I NOT like about it?
* From the manual: "Warning: When charging finishes, pull out the charging cable." Why? Does it lack overcharge protection? I doubt it's a fire hazard, but will it degrade the battery?
* There are gesture instructions printed on the touchpad surface. That's unnecessary, and unattractive considering how sharp this keyboard looks otherwise. But at least it's printed in white, so it's tasteful.
* It has a built-in microphone, but no instructions on how to use it. The mic doesn't seem to register Windows 7. I haven't tried on my tablet or Pi because I really don't care. I needed a keyboard, not a microphone, and every device in my house that needs a good mic already has one. I would prefer that Rii drop the mic altogether and add overcharge protection.
These are pretty weak cons and no reason to dock this product any rating stars. I heartily recommend this keyboard.