Apple has taken the iPhone to the next level and added some excellent features, including 3G/HSDPA, GPS and support for Microsoft Exchange email. You still can't send MMS and there's only a 2-megapixel camera, but overall it's a wonderful experience.

The iPhone 3G is available from Apple, Carphone Warehouse and O2's online and high-street outlets. You can buy it on a monthly contract, starting at £30 a month with a £99 upfront charge for the 8GB model, or £159 for the 16GB model. You can get it for free if you pay more than £45 a month. Alternatively there's a pay-as-you-go option too, if you'd rather not be on a contract, but Apple hasn't yet announced the price.

Design
When you open the lid of the iPhone 3G's compact box, at first sight it looks little different to the original iPhone. The front section is indeed very similar to its predecessor — the screen is the same size, the ear speaker and home key at the bottom look the same and the silver rim around the edges is the same as the old one too.

But when you take the iPhone 3G out of its box, you start to notice the differences. The back section features plastic instead of metal and curved edges similar to the MacBook Air's. Technically it's thicker than the original at its thickest point, but the curved edges genuinely make it feel thinner. You'd expect it to feel more flimsy, but the type of plastic used makes it feel quite solid — we do expect it to get scratched though.

Another design difference from the original iPhone is the headphone jack. The original iPhone features a recessed jack, which only allows you to use headphones with pins that fit through the gap. The iPhone 3G's headphone jack is flush against the edge, meaning you can plug in any headphones, which will make a massive difference to the sound quality you can enjoy.

Overall, the feel of the iPhone 3G is, as expected, superb. It feels just how you want a smartphone to feel. It's neither too heavy nor too light, it feels solid without being overly bulky, and the screen — almost identical to the original iPhone's — is a joy to behold.

Features
When the iPhone first appeared, many were disappointed by its lack of 3G, among other things. Apple has clearly fixed this — in fact, it's gone one better and included HSDPA, which takes 3G's 384Kbps download speed up to 7.2Mbps. And it makes a massive difference. Browsing the web and watching YouTube videos is lightning-fast compared to the old iPhone, which was limited to GPRS/EDGE speeds. We loaded the Sky News homepage on the original iPhone in 1 minute 40 seconds: the iPhone 3G took just 40 seconds to load the same page — 2.5 times as fast.

GPS is another notable addition to the iPhone 3G's artillery. Compared to the original iPhone's cellular and Wi-Fi triangulation, GPS on the iPhone 3G is far more accurate — GPS pinpointed our location to within metres rather than kilometres. For the time being it only works with Google Maps, which doesn't do voice navigation (some pundits have suggested that Apple isn't keen on third-party developers creating navigation apps, but we'll have to wait and see).

As for other applications, you'll be glad to know that the App Store is live and already features over 500 programs. You don't need to use the badly implemented web-based apps anymore, or unlock your iPhone. Some of the apps come free, while others you'll have to pay for.

Apps range from simple games to internet radio stations, and it's extremely easy to download them. All you have to do is click on the desired app and it pops up in your iPhone 3G's menu, installing relatively quickly, depending on the size of the file. Most of the free apps aren't very useful, and some are frankly bizarre (such as an alarm that doesn't have a timer), but as the App Store increases in popularity much better free apps are sure to appear.

As an iPod, there's little difference in sound quality between the original iPhone and the new 3G version. However, the iPod classic, for example, offers a slightly warmer sound and is a better performer in our opinion.

For businesses, the big news about the iPhone 3G is that it supports Microsoft Exchange. This lets you synchronise all your office emails, contacts and calendar entries over the air. You can also view Microsoft Office documents, but you can't edit them, which is frustrating.

Although there are plenty of improvements on the iPhone 3G compared to the original model, we're still disappointed to see that not all of the old problems have been resolved. The iPhone 3G's 2-megapixel camera isn't an improvement on the old one, there's no flash you still can't shoot video. MMS messages are still unavailable and there's no stereo Bluetooth to let you listen to music wirelessly.

Some of these issues may be resolved with third-party apps, but the lack of movement in these areas is disappointing to say the least. In our opinion those are basic features that should come as standard on a high-end smartphone. On a similar note, given the iPhone 3G's spec, we also think that a VoIP client should come with the new firmware to facilitate a cheaper way of making voice calls.

Performance
The iPhone 3G vastly supersedes the old iPhone in terms of audio quality during calls. You can hear callers loud and clear, with no noticeable distortion. The iPhone 3G's loudspeaker is also louder than its predecessor, but still not as loud as we'd like.

We haven't had the iPhone long enough at this point to properly test the battery, but from our usage so far, we think it should last for around a day with moderate use of 3G and GPS. We'll update this section when we've exhausted the battery. There is an option to turn the 3G off if you want to save power. It's annoying that the battery cover still can't easily be removed, however.

Conclusion
The iPhone 3G is still hampered by a few minor problems such as the inability to send MMS, but overall we found it a joy to use. What it does do well is so far in advance of other smartphones you almost forget its downsides.

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