I had a map of 32GB Class 4 for my HTC Desire smartphone with Android 2.3.3. I placed a part of the operating system on the micro-SD card and the phone often planted. I had doubts about the speed of the micro-SD card, and I bought Lexar class 10. Since then, my phone works fine in the same configuration. I did not measure whether the performance of the card correspond to class 10, but the difference is very clear compared to the previous card. The card reader works well and is very fast with the card.
