I just got the VZW XV6700 and am now in the market for an SD card for obvious reasons. My dilemma is that there are a few different speeds ranging from unmarked (4.5 - 7.85 MB/sec read rate for the Kingston) all the way up to an ATP card rated @ 150x (22.5 MB/sec). My question is can the card reader actually support such high read/write speeds or is it just going to offer diminishing returns to go past, say, the 60x (10MB/sec) cards? Anyone tried out the higher speed cards vs the standard cards and noticed any performance difference?

I would say no. Smartphones don't take advantage of it like a camera would.

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My sordid past:

Kyocera 6035, Kyocera 7135, Samsung i700, iPAQ 6315, iPAQ hx4705, Motorola a630, BB 7100t, iPAQ rx3115, JAM 850, BB 8700g, Samsung i320 (just for fun), imate KJAM, TMO SDA, MDA, TMO Wing

That's kinda what I was thinking... The 60x is basically the same price as the non-high-speed one so I'll probably just go that route and save the $12 premium the 150x carries.