If you've been hesitant to update your IOS version, you now have an excellent reason to do so. At least if you're an AT&T customer. Updating from the base revision on a new iPhone4s (which, I believe, is 5.0.1) to 5.1 or up will make your phone use 4G (LTE) instead of 3G (UMTS). If you turn off WiFi (because it crowds the screen at the top left) you'll see whether you're running 3G or 4G. If you're 3G and upgrade, after the update you'll see it say 4G instead. So all you data access will be an order of magnitude faster than 3G, owing to the greater bandwidth (and lack of users) on 4G. That said, everyone should be aware that, when making a call on 4G, you'll fall back to 3G using "Circuit Switch Fall Back" to handle your call.