The iPhone 4 is the fastest, most responsive device in the market. The 1GHz processor and 512MB of RAM have made a huge different in its ability to open and run applications quickly. It has HSDPA/HSUPA radios inside, and can access faster download/upload speeds. In my simple tests, I reached a max of 3.1Mbps download and 879Kbps uploads through AT&T's network. The previous best-case I ever saw with the iPhone 3GS was 1.8Mbps up and 634Kbps down.
The iPhone 4 also has 802.11n Wi-Fi. Even though it is limited to the 2.4GHz variety of Wi-Fi, it is still capable of faster surfing speeds with the proper Wi-Fi equipment. In my speed tests over 802.11n Wi-Fi, the iPhone 4 reached download speeds of 7.44Mbps and upload speeds 4.05Mbps. Real-world translations? You can share pictures and videos much faster.
Battery life has been great so far. I brought the iPhone 4 to a full charge by Noon on June 24. At 3PM on June 25, the battery still had 56% left. I have Gmail synced via Exchange. I've spent hours browsing the Web; have watched some video; shot about 50 images; and captured 5 minutes of HD video footage. The iPhone 4 indeed improves upon battery life.
In the 30 or so hours that I've been testing the iPhone 4, I haven't dropped a single call. This experience is going to vary on many, many conditions. The quality of calls is somewhat improved for several reasons. Apple has improved the noise-cancellation abilities of the iPhone 4. It now has two microphones: one to capture the sound of your voice, and another to listen to background noise and filter out extraneous sound. It works. The earpiece of the iPhone 4 is also louder than its predecessors. This is very good news. It doesn't compare to the excellent Motorola Droid, or amazing Nokia E73, but it is much improved. The speakerphone is also much louder than before, and will be a much better tool in the office than it was before.
Apple says iOS has over 100 new features. Finding some of them can be tough. The basic user interface of the iPhone is the same and so are many of the base applications. . . and that's probably the iPhone 4's biggest weakness.
Android -- and to some extent webOS -- have surpassed Apple's iOS4 in features and functionality. Take social networking, for example. Android has support for Facebook at the API level, which lets developers do all sorts of interesting things. For example, the way Android handsets can sync not only profile photos, but information, status updates, and messages between Facebook and the contacts application is interoperability that needs to happen on the iPhone. Instead, Apple relies on third-party applications to cover a lot of the bases that it skips.
Android offers far more flexibility and customization to the end user. iOS4 recently added the ability to pick wallpapers behind the home screen applications. Android has supported that from day one. Android also supports widgets. Widgets can be used to place controls directly at the fingertips of users rather than buried deep down in settings menus as on the iPhone. Android also supports shortcuts to performing certain actions. For example, users can place a shortcut on the home screen that with one press will call a specific contact from your database. Apple needs to take social networking more seriously. Its competitors do, and some have already outpaced Apple with innovations.
Apple has crafted a fine device. The iPhone 4 easily surpasses the iPhone 3G/3GS in terms of design, performance, and capabilities. Where Apple use to be the leader, however, it now has peers. Android, in particular, has caught up to iOS4 quickly and in many ways is superior. Research In Motion is set to debut its new operating system in the coming months. Under HP's ownership, surely Palm will kick out a heavily revised version of webOS by early 2011. Apple needs to make more drastic improvements to iOS5 if it wants to stay well ahead of the competition.
If you're looking for the best Web-browsing, best gaming, and best media consumption device, the iPhone 4 is the clear winner.