[ladyada]

Good question! I test all the products in the adafruit shop for quality and functionality :)

I tried out half a dozen 5v/1a adapters and this one was the winner - best performance and a very good price for UL listed. The most important points: It has the 'iDevice' resistors and has very good voltage regulation - extremely clean, no big voltage spikes. When loaded down 1A it stays around 5.2V, I actually pulled 1.5A and it was still above 5V. I opened a few up to look at the construction and found it well designed with good soldering, strain relief etc. In the product description I explain why its a 5.25V not 5V adapter - its perfect for high-current devices like the Raspberry Pi and we have thousands of customers who have happily used it for the Pi.