Backward compatibility is really important to me. So my main testing device is an iPad2 with 512M of RAM with the OS usually taking at least half of it. Yep that ain't much. Any device with 768 pixel or less in height (like my iPad2) get the low res sprites which are using 4x less memory than the high res (optimized for 1536px). Overall, I think it should run correctly on most devices.