It may not sport a bigger screen or a different design, but the iPhone 4S is certainly a step on from itspredecessor, although much of the attention will be focused on just how big that step is.

Sporting the already-lauded A5 processor, improved aerial signal and a better camera, the hardware changes to the iPhone 4S from theiPhone 4 are by no means striking. It's difficult not to feel a little underwhelmed that an incremental increase has been 16 months coming.

You can check out our iPhone 4S video preview, complete with a look at the new voice controlled Siri software:

However, the Siri personal assistant software is likely to capture the headlines, the photographs we took with the new 8 megapixel camera may well convince us to throw away our compact camera and the big improvements in graphics and processor power could lead to some enticing opportunities.

We're not going to dwell on the design of the device – it's identical to the iPhone 4, so check out our hugely in-depth review to see how the hardware handles in the hand.

Siri-ously

It is Siri that raised the temperature at the launch event more than any other feature, so it seems that the personal assistant is the natural place to start.

Voice control is by no means a new concept, but interpreting what has been said and working out the context is something that has not been fully explored on a mobile device before.

Google is doing great work with its own voice software, but Siri appears to have taken things - for now at least - to a new level.

Why? Simply because it seems remarkably good at interpreting instructions and turning them into actions.

Siri isn't integrated into everything that the iPhone 4S does, but it does link up with some key features, allowing it to be a significant tool and not a cheap gimmick.

Demanding Siri to, for instance, set up an appointment for 9am on Friday not only creates the appointment, but checks first if you are free and tells you if you have a clash, offering the chance to change your mind.

Asking for a Wikipedia search brings the information fast, and the Wolfram Alpha integration means that you can get precise answers to mathematical problems and to things such as currency and weight conversions.

The feature also integrates into the new task list in iOS 5 (more on that later) which means you can set up action points not only for times and dates, but also when you leave a 'geo-fenced' area.

For example, asking Siri to set a reminder to buy your wife a card when you leave your workplace will do just that. It's a powerful mechanism and one that moves from 'cool, but something you won't use after trying it once' to 'actually something useful'.

There are also some slighty twee but satisfying Easter eggs. Ask Siri who she/he is brings up "a humble personal assistant" asking it the meaning of life was met with "To answer questions like these". (Although the obvious answer is 42, right?).

It's a very nice integration of something that any sci-fi buff has been expecting on their personal communicator for some time now. And although even Apple is clear that it's not perfect, it is a tool and not just a fad.

Of course, whether you can get over looking like a madman or a tool by talking to a robotic-voiced device is another question entirely.

Aerial threat and happy snapper

Moving on, Apple is also keen to point out that the aerial issue that tainted the launch of the iPhone 4S' predecessor – the iPhone 4 – is not likely to be repeated, with dual aerials in the 4S that can automatically switch to bring a faster and more stable signal.

We can't actually tell you if this is noticeable yet, because we were only able to use the phone on Wi-Fi, but we look forward to testing this out in our fulliPhone 4S review later this month.

The camera is certainly an improvement; backed up by a very good processor and a decent sensor, along with some interesting software options, the snapper on the iPhone 4S will convince some that the time is ripe to only buy a DSLR for holidays and rely on their smartphone for everyday photo tasks.

8MP snapper: A shot from the iPhone 4S camera

The video camera is now capable of filming in true HD 1080p; given the iPhone 4's video functionality was laudable, this means that flip cams and even cheaper video cameras might need to watch their rear viewfinders.

However, don't think this is anything revolutionary - it's still only keeping pace with the imaging capabilities of the likes of the Samsung Galaxy S2. And the low-light capabilities of the iPhone 4S are yet to be proved better than the Exmor R sensor in the Sony Ericsson Xperia Arc S.