I have a Carsifi dongle, and really I don't have anything but praise for it. Bought it a couple of months ago, plugged it into the car's USB port, and then paired it with my phone, and I've rarely thought about it since - which I think says a lot about how seamless it's been. I get in the car, the phone connects and Android Auto comes up on the headunit. If you didn't know the dongle was plugged in, you'd just assume the car supported wireless AA from the factory. And the dongle itself is tiny, so it's easy to forget it's there. About the size of a matchbox, but thinner, and it was provided with sticky pads and a short USB cable. I have it mounted neatly in the cubby under the armrest, right next to the USB ports.
It comes with a companion app (not mandatory) which enables some advanced features. You can set adjust the DPI value which used to be useful for fooling AA into thinking my car's screen was bigger than it was, which in turn forced it to display in split screen - however, since Coolwalk, this isn't necessary anymore. There's also a feature to suppress the regular safety taps from being required, and the app will also allow firmware updates. The dongle also has a physical button which will allow you to switch between multiple AA phones connected to it (I haven't used this yet).
So far, no reliability issues. No disconnections, hangs, or failures to connect. No noticeable lag. Really, I am struggling to find any fault with it. The only "downside" I can think of is that it takes a little longer to connect than when plugged in with a physical cable. But even that is being really picky - we are talking maybe 10-15 seconds at most for AA to load. It's generally ready to go by the time I've got comfortable and have plugged my seatbelt in.
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