Also worth noting from the link in my previous post that the 1800x 64GB is even faster. I can't imagine there being any lag at all at these speeds.
64GB—up to 270MB/s read, 250MB/s write
How about the new Lexar 1000x or 1800x cards? Surely no lag at these speeds?
1000x - up to 150MB/s read, 90MB/s write
1800x - up to 270MB/s read, 110MB/s write
microSD