I did a further test on a modern low-end digital SLR camera (Nikon D50), and found that the 60x speed-rated (this refers to the write speed, not the read speed) cards are slightly faster than their non-speed-rated brandmates, but not by as much as the memory card manufacturers lead you to believe. With continuous shooting of six compressed RAW images, the 60x cards (from Lexar and Sandisk) took about 10 to 11 seconds (from first shutter release to the completion of the writing), while the slowest non-speed-rated cards (of those that I have on hand) took nearly 16 seconds. Two blue non-speed-rated SanDisk SD cards proved to be either "fast" or "slow," depending on the capacity of the card (the 1GB card, with a RAW shooting performance time of about 12 seconds, performed more like the 60x cards in my testing, while the 256MB card is more like the "slow" PNY 2GB card). What's more, the results show very little correlation to the TRT results with a card reader connected to a high-performance PC.

Please note that the above performance results are relative. The 60x SD cards are the fastest SD cards that are available from most big-box retailers like Wal-Mart, Best Buy and Circuit City. You'll pretty much have to buy 133x-rated SD cards from a large camera store or an online reseller.