I have been playing 1080p video fromon the iMX53 QSB using the supplied Ubuntu demo OS, and the video plays back very nicely indeed. The SD card is a Kingston 4GB class 4. When I build the BSP on my own unbranded 8GB class 10 card it also plays back fine, but I notice on some 'zoom in' parts there is a very slight stuttering. I wonder if you folks have any idea if this could be to do with a difference in the SD card somehow, or if it's more likely to be processes running on my BSP build which are not there in the other demo card? Are there any general opinions on whether a faster 'class' card is worthwhile, and whether branding makes much difference?