LOL I just found out that CPU used by the Nokia X series isn't similar to the Lumia 520 at all.

Nokia X uses MSM8225 (dual core Cortex A5 and Adreno 203 made on 45nm), Lumia 520 uses MSM8227 (dual core Krait and Adreno 305 made on 28nm).

So the CPU alone is half as powerful as the CPU in the Lumia 520, and GPU is of the previous generation. Windows Phone 8 currently couldn't run on this hardware even if Nokia wanted it to.

At first I was curious about the Nokia X phones, now I will definitely wait to see reviews. Single thread performance on the Cortex A8 in the N9 is better than on Nokia X. That combined with a relative old Android version will most likely result in bad performance, but I'll wait for the reviews to see this confirmed