With this product being so cheap, I wasn't expecting it to be fantastic, but with shop versions (Halfords etc) ranging from £10-£20, I figured I didn't have a lot to lose.
As it was, I have been pleasantly surprised. It works absolutely fine. It charges while the SatNav is being used and hasn't set my dashboard on fire yet. The only slight gripe is that the charger itself sticks out quite along way from the cigarette lighter, which means my hand sometimes catches on it when I change gear, but it's not really an issue.
A product that does exactly what it's supposed to do, delivered quickly and on time and for a fantastic price. You can't really say fairer than that. Highly recommended.