Agree completely, when using the SD card for recording photos or videos on a camera, a linear steam of writes, the class speed is helpful. When using it as a filesystem or swap space, like in a smartphone, tablet or netbook, random I/O speed is the most important factor to me!

My class 2 Sandisk card was (perceptively) much faster than class 10 cards I tried from other manufacturers (and which cost twice as much). Tests have shown over time than Sandisk, while never competing on class speed, are consistently king of the random I/O speed.

Hopefully they continue that trend with their SDXC cards!