For me, where I notice the speed lag the most on my 3G is in switching from one app to another, i.e. out of Mail and into Safari - and page rendering in Safari. Twice as fast would be very nice! I don't get to replace it until March next year, by which time maybe there'll be a 4-letter iPhone in the works? 3GSi or something smile.
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If it's brokenless, don't suffix it...