Evaluating a product is always one of the more difficult tasks for a writer. Everyone has their own individual preferences, and the reviewer is forced to pool these together, stir them up, and distill a complex personal experience down to a few paragraphs someone will use to decide where to place their hard earned dollars.
Apple didn't make this any easier by combining the release of the iPhone 3G and iPhone 2.0 software for first generation iPhones over the course of two days. Well, it was supposed to be a single day, but Apple's server overload disrupted that plan. Even so, the company reported today that were sold worldwide between Friday and Sunday, and more than  during the same period. (To quote Red Sweater Software's , "If I ever sell a million of something in 3 days, I expect to see some infrastructural problems, too.")
Rather than write a comprehensive review of the iPhone 3G and the iPhone 2.0 update - which were released on Friday - these are just my first impressions.
The Hardware -- Although the iPhone 3G is only slightly wider, the design of the bevel makes it feel overall thinner and wider than it actually is. Aesthetically it's an improvement, but this is like comparing two supermodels. The 3G is definitely sleeker in feel, and the metal buttons (power, volume, and ring mode) in the black plastic are a nice touch with a really great feel. The speakers on the bottom are smaller, but with metal grills rather than the usual tiny holes punched in plastic.
In subjective testing, the volume of the 3G is probably equal to the original iPhone, but with better sound reproduction. At full volume it sounded less tinny and more like regular speakers, but it still won't shake down the walls of the house. The camera is the same resolution (2 megapixels), but photos seem slightly better on the 3G, although they still lag higher resolution options.
The much-lauded non-recessed headphone jack is exactly what you'd expect, and it's nice not to have to carry a little adapter around for workouts or car connections anymore. The plastic case is pretty tough, surviving an accidental drop test with just a small scratch when it slipped out of my pocket during a movie.
3G and GPS -- The star attractions of the iPhone 3G are its increased data speed and inclusion of a built-in GPS (global positioning system) chip. The 3G connection is noticeably faster than EDGE, and the overall reception of the phone seems better. Testing in areas with spotty reception shows the 3G holds better signals - something we frequently get to test thanks to AT&T's network. Web browsing is easily double the speed of EDGE so far in my testing. It doesn't match Wi-Fi performance, of course, but it's still quite satisfying.
The iPhone 3G is now location-aware thanks to the GPS, which, in combination with cellular triangulation and location information from Skyhook (which maps Wi-Fi networks) is truly outstanding. (The first-generation iPhone uses only cellular triangulation and Skyhook to establish location.) When you switch to the Maps application, you quickly get a large ring with your general location, followed within seconds by a pulsing blue dot at your exact position.
Early reports suggested the GPS wasn't accurate enough for turn-by-turn directions, but I found it to be both surprisingly accurate and much faster than starting up a traditional GPS device. One of the worries about GPS is where to put the phone in order to get the best reception, but the iPhone 3G managed to hold an accurate position even while being handheld in the car, where GPS signals are notoriously weak. It appears accurate enough to feed audible turn-by-turn directions should Apple authorize a third party navigation application; Apple's developer agreement stipulates that developers cannot create such an application.
One of the best features of the 3G radio is the capability to make phone calls and use the Internet at the same time. Aside from letting you look up movie times while chatting with your friends, you can now use the GPS and Maps while talking on the phone. That's perhaps not the safest thing to do while you're driving, but at least you'll know exactly which lake you just ran your car into while being distracted.
On the downside, as Apple warned, the 3G radio consumes a lot more power than EDGE, leading to a noticeable decline in battery life. I tend to travel a lot and really pushed the battery on my first generation iPhone, but could usually make it through a business day. After a couple of days of testing, it was clear I'll need a portable battery pack to survive my trips with the iPhone 3G. (I ordered the, which looks compact enough to carry in my bag, and unlike some other external batteries can directly recharge the iPhone.)
The iPhone 2.0 Software -- Having tested the iPhone 2.0 firmware on both a first-generation iPhone and the iPhone 3G, the performance appears completely equal aside from network performance. Apart from MobileMe and the App Store, many of the changes are small, but welcome. You can finally bulk-delete or move mail messages; a Contacts application takes you to the same contact list used by the Phone application; the Calculator application becomes a scientific calculator when you turn the iPhone into its horizontal position; Calendar finally supports multiple calendars from iCal (although strangely the colors you assign to calendars in iCal aren't honored); pressing the Home and power buttons simultaneously captures a screenshot and saves it to the Photos application. Two much desired features, cut-and-paste and support for iCal to-do items, are still noticeably lacking.
The App Store application is well designed, making it easy to move between different categories and find software. (The App Store also appears in iTunes.) Application user ratings are included right in the store (although, oddly enough, not when browsing applications in iTunes). One really nice touch is that the App Store checks for software updates to your installed applications; the App Store icon on the home screen will indicate how many software updates are available. Purchasing titles is easy, and fortunately requires your iTunes account password before you're charged or before a free application is downloaded. The new application's icon immediately appears on the home screen with a little status bar showing the installation progress.
The downside of the App Store is that not all applications are created equal. Many applications, such as AIM or The New York Times reader, seem plagued with early performance issues and frequent crashes. Some of the location-aware applications in particular seem to lock up or crash location services, requiring a system reboot to regain use of Maps. There's also no shortage of... marginal applications.
But complaining about a few bad applications and the occasional crash seems almost selfish once you realize how game changing third party application support really is. Want to find a movie? Load up and see times for anything within a 5 (or 10, or whatever) mile radius of your current location. Don't know where the theater is? You're only one tap away from directions and the GPS-enabled Maps. Traveling, have no idea where you are, and need the weather?  will give you the forecast for your current location. Want to race prehistoric cars or cute monkeys in bubbles? Stream Internet radio? Dictate a to-do item and have it transcribed to text and added to your calendar? The App Store has you covered. (The links here go to the iTunes Store.)
Spending just a few days with the 2.0 update and the App Store really gives you a taste of the future of augmented reality - where the phone becomes far more than a communications device or occasional portable game machine. And remember, all these capabilities, except for the pinpoint location provided by GPS, are available to anyone with a first-generation iPhone or iPod touch.
Final Impressions -- Overall, if you compare an iPhone 3G with its first generation predecessor, the user experience is very similar. Many first generation users will be more than satisfied with their 2.0 update, which is where most of the changes are. You'll still have full use of the App Store and even location services (although without the same accuracy).
But for heavy data users or frequent - and directionally impaired - travelers, the iPhone 3G is a welcome upgrade. Internet access is materially faster, and the GPS is accurate, useful, and well integrated into various third party applications. If you have a first generation iPhone and are happy, there's no need to upgrade, but the 3G is still a worthy second version of an exceptional product.