I just got my new T-Mobile Vibrant (branded Galaxy S) and love it! I'm a "newbie" to an Android phone, so please correct me where I get it wrong. I hope the info I tracked down on microSDHD speeds may be helpful. In a nutshell ... According to the "Galaxy S Premier Support" person (she told me she was "as high as I could get" in the Samsung tech support hierarchy): -- The Galaxy S can take up to a 32GB microSDHC card. (My manual says only 16GB.) -- A "Class 6" microSDHC card is about the max speed needed for use by the Galaxy S. I'm not sure she really understood my question, which was: What is the fastest class that the Galaxy S can write to and fully use the card's speed? I explained that I wanted the fastest card that the Galaxy camera and video could exploit, but didn't want to waste money on a higher-rated (and more expensive) card that would provide no performance advantage. -- I note that the Kingston Web site shows a Class 4 as the right speed for cell phones, but this may be considering Internet download speeds, not camera and video. However, the same table shows Class 6 as the right speed for high-end cameras and video. -- It's VERY important to realize that the SD Association sets the specs for the "Class" standards, but manufacturers can just claim they meet a certain class performance without any independent verification. Caveat emptor! Similarly, some cards appear to significantly exceed their stated Class. These can provide "hidden" deals, so it pays to look for actual performance tests. HTH. In the end I made my own tradeoff of capacity, rated speed, and manufacturer's reputation by getting a Kingston 16GB Class 4 for under $40. After a while, when 32GB Class 6 cards become more afforable, I'll get one and use the 16GB as a spare. -- Paul P.S. Did I mention I LOVE this phone!