Apple's new CEO Tim Cook had big shoes to fill after Steve Jobs' departure last August, but yesterday's iPhone announcement provided the executive a chance to step into the limelight. Contrary to what many were hoping, however, the iPhone 5 was a no-show at the event, so no bigger screen and no slimmer profile. Instead, the iPhone 4S is an incremental update to the iPhone 4 that keeps the same external design with new hardware under the hood. This is comparable to what we saw when the iPhone 3G was succeeded by the 3GS. Apple has included some worthy upgrades to the venerable iPhone 4 that will go a long way towards luring many new buyers as well as upgraders. If you're on the fence regarding yesterday's update and what it means for iPhone users, here's what you need to know.