@rickyw88, unless you are having problems reading and writing to your card, I wouldn't waste my money. I have used a class 4 and a class 10 micro SD cards on my 2Din GPS and I could not tell any difference in performance. In addition, I had my old MIO GPS running side by side with my 2Din GPS and again, both ran practically simultaneously and identically. As long as your GPS can read reliably your SD card, it doesn't matter what is the speed of your SD card. Just to make it clear, I am not talking about a low quality reject no brand cards.

My understanding is that all critical navigation processes are performed in RAM, therefore the SD card speed is immaterial. Also, the boot up time of identical Primo on my MIO GPS and the 2din GPS was also almost identical. BTW, my old MIO GPS processor runs at half the speed of my 2Din and its SD card is an old 2GB before they even started labeling the speed of the cards.