Quite some time ago I bought a couple of these devices so I could watch streaming TV on the TV without tying up a mobile phone or tablet, and needlessly flattening its battery. In that regards, it's quite good. You can hand over something you've chosen on your phone, and it'll take over. You can use its remote (most of the time) to control it from there on.
But where it fails…
Quite often you will lose control, it will carry on doing its thing no matter what buttons you press, and you'll have to pull the power plug out to stop it.
The remote is far too tiny to be comfortable in adult hands. You're contracting all your fingers into a tiny space to hold it and use it.
It's ridiculously slippery. You put it down on the couch next to you, and it just skids away. Usually it skids towards you, and you end up sitting on it, pressing some of the buttons.
Many of the buttons are far too light-touch. You end up pressing them accidentally picking it up, or feeling for the right button. I'm sick of accidentally hitting the Netflix button when grabbing the remote whenever some obnoxious advert comes on.
After a while, some of the buttons stopped working properly (you'd get no response, you'd have to press very hard, you'd have to press several times, sometimes one press would be treated as several presses). This could be due to flattening batteries, and due to bad luck the device is worse at handling some switches when the batteries are too flat (that does happen with some remote controls). It certainly won't be fixed by re-pairing this bluetooth remote control with the dongle on the back of the tv (that's the same stupidity as people who believe that re-installing Windows software over and over fixes its faults, if the remote needed to be re-paired with the device, none of the controls would be working). It is far more likely to be due to bad switches, and it certainly was in my case. More about dealing with that in a page on dissassembling the Google TV remote, but this has been a common problem with TV remotes ever since the first electronic remote control was invented.
You are limited in what apps you can install. No surprises there, many apps would have been designed for touch screens, and only for specific versions of the Android operating system. But there are some obvious TV streaming ones that you'd expect that there should be a compatible app for them (like Dailymotion).
And one of its prime apps, YouTube, loves to stuff up sound playback so its completely mute until you reboot it, or make some blood sacrifices to a pagan god.
Interesting, useful most of the time, but badly flawed.