Apple's design and hardware changes are all rather impressive, and despite adding more CPU horsepower, Apple has managed to improve battery life over the prior iPhone models. We wish that they would've taken the opportunity to add physical Orientation Lock and Camera Shutter buttons to the edges (the button layout around the edges is effectively the same as on the iPhone 3GS and 3G), but those are minor quibbles in the grand scheme of things. The phone's new display is simply awe-inspiring and gorgeous. Apple has once again set the bar for mobile displays, even besting their own iPad display perhaps in some ways. With a 960x640 resolution, the Retina Display is as sharp as a tack and as smooth as any screen we've ever seen. It's also exceptionally responsive, with any and all multi-touch gestures being recognized immediately. We can't say enough about how spectacular the display is; oftentimes, Apple's claims can be overblown somewhat, but the display really is every bit as good as Apple says it is.
There's really not a lot to complain about if you're already an existing user of the iPhone. There are only improvements to focus on, and while there are still areas where iOS doesn't quite live up to Android (the ability to customize the lock screen, view the past six opened apps, enable tethering / mobile hotspot without carrier interference, etc.), iOS has closed the gap in a big way. We still think that Android 2.2 is a worthy opponent, and in some ways, superior. But the iPhone 4 will no doubt be a huge success for Apple. It simply "works," and it's extremely easy to get into and understand, despite that typical Apple limits are still in place in some areas. This may or may not be the case for some less sophisticated users, with respect to the Android OS. Regardless, somehow, Apple has made the act of multi-tasking easy, and the ability to categorize apps into folders adds a level of utility that isn't available on any other mobile OS.
To say that the iPhone 4 is one of the best smartphones on the market would be understating things. It has the nicest smartphone hardware we've seen to date (largely thanks to the Retina Display, which is unrivaled at this point), and the new operating system is extremely robust. We doubt any potential iPhone 4 buyer will walk away disappointed, and if you're an existing iPhone 3G or iPhone 3GS owner, you'll likely be thrilled with the upgrade. It's faster, sexier, more robust and more functional. It's an upgrade in every sense of the word.
The main thing that you should consider before buying into the iPhone 4 isn't whether you'll be pleased with the phone. Its speed and incredible ease of use leads us to believe that most everyone will find something to like about the new device. But being stuck on AT&T for two years is something to ponder. There are so many excellent Android phones available on Verizon Wireless, T-Mobile and Sprint right now, and AT&T's dropped calls and overloaded network issues are not just myths. AT&T also has a smaller 3G footprint compared to Verizon. Worse still, AT&T is no longer offering an unlimited monthly data plan for $30/month; instead, new customers will only be given the option of cheaper, albeit more limited, data plans. And if you want to add Internet tethering, you'll have to switch to one of the new plans. Existing smartphone users on AT&T can opt to keep their existing plan, but only if they don't want tethering.
If you live in a major city with solid AT&T 3G support (and you don't travel to rural areas often), there's still probably nothing keeping you from selecting the iPhone 4. But if your area is known for spotty service, or if you travel frequently to areas with coverag issues, you may not be able to fully enjoy the features of Apple's latest smartphone. To us, the carrier is the biggest decision in whether or not the iPhone is for you; if you get great AT&T service and are okay with the available service plans, the iPhone 4 is a real winner. Otherwise, you'll probably want to look at HTC's DROID Incredible, EVO 4G or one of the other fantastic Android options on one the other major carriers.