I am about to step up to a Canon 7D from my Xsi. The 7D uses CF cards instead of SDHC memory card, which I own about 100 worth. I want to purchase several cards, as I am always afraid I will never have enough (I'm stange that way). Now, here comes the question; What are the best to buy? I understood the "class" ratings of the SDHC cards, but are lost when it comes to CF cards, even after doing many google searches. All Canon says is "CF Card Type I and II, UDMA-compliant CF cards". Any suggestions or guidance?