As accurate as any, with attractive GUI

My admittedly nonprofessional experience with this kind of app is that none are perfect. They give different results based on a number of variables.

That said, Speedtest X HD gives results that are absolutely consistent with other similar apps, including the FCC and Speedtest.net versions (iPhone), as well as several websites Ive used on my Mac. However, this app has an attractive iPad GUI which the others lack. While that doesnt affect the accuracy, it does make it more pleasant to use, so it is the one I use most. (I do wish it worked in portrait mode, though.)

After using the free version for a time, I happily paid $.99 for the "Pro" version in order to support the developers efforts.

John424 about Speed Test SpeedSmart Internet, v7.4.0