This review shall be based on the working order of my iPhone after having it for two years, but I shall also note on the differences between now and when I first received it.

What is it?
The iPhone 3GS is a Smartphone developed and produced by Apple Inc which was first introduced by the company on June 19, 2009. Over the first weekend this product was able to sell over 1 million units and over 37 million overall.
Though still possibly the most popular choice of iPhone since the iPhone 5 has been released the iPhone 3GS has since been discontinued.

Operating System
The current Operating System for all iPhone Devices excluding the iPhone 2G is iOS 6.0, this particular Operating System takes up 23% of the phone's data memory just by being on the phone, but is necessary for advantages such as iBooks, Folders, News Stand, Game Center, Notification Center and unfortunately the disappearance of the built-in Youtube option, forcing all iPhone users to download a Youtube App which luckily has ended up working a lot better.

Price
Because of this product being discontinued I am unable to tell you exactly how much the price of it was, but if I remember correctly for 8GB it was around £400 for £16 it was around £420 and for 32GB it was around £450.

Weight
The weight of this device is 135g.

Look of the Device
In my personal opinion I believe the iPhone itself has a very sleek, sophisticated look unlike it's rival Blackberry, a lot of people believe the Blackberry looks more like a professional business phone, but I disagree I would chose the look of the iPhone any day.

Screen
The iPhone 3GS has a Multi-Touch Touch-screen display with the dimensions 7.5cm x 5.5cm, the screen is extremely sensitive to human contact which can occasionally cause issues when using the device, for example although these may sound petty and not really a problems they have been extremely frustrating for me personally:
-Occasionally when I go to enter my passcode I will press the key slightly to close to another and end up having to type it in again and again.
-When I'm listening to Music I will accidentally tap the iTunes store button and be taken completely out of the iPod section.
-When I'm playing apps and a pop-up appears I will accidentally tap that and again be taken completely out of it.

Keyboard
The Keyboard for iPhone 3GS is a Touch-Screen Keyboard consisting of all the necessary keys of a keyboard, generally I find this keyboard much easier to use compared to say a keyboard with three letters on each key or a Blackberry Keyboard.
The only Glitch I have found with the Keyboard is that it can occasionally freeze to the point where you have to restart your device but this is very rarely.

Camera
The iPhone's camera is a 3.5 megapixel camera with option to zoom in and out and take both pictures and video , I myself find that it is very good quality and I have successful taken some professional looking photo's with it, however in using the iPhone to record gigs or performances I have found that the sound will prove to much for it and the microphone will just block it out, which is a real shame, apart from that the only other thing is that it sometimes has trouble focusing.

Apps
There are a range of Apps to choose from such as Games, Photo Editing, Social Networking and lots more and they are all available to this device the only apps you aren't able to access and the ones made specifically for iPhone 4, 4S and 5.
Occasionally Apps will freeze, but remember I've had my phone for over 2 years.

iPod
The iPod section on the iPhone has a very neat layout with the choice of Album, Artists and Songs, it's easy to understand and arrange, plus music takes up a lot less room than photo's so it's much simpler to upload the variety of music that you desire!

Assessibility
As soon as I received my iPhone I instantly understood how to use it, so personally I would say this device is extremely easy to use.

Internet
The Internet Provider on iPhone is obviously Safari seeing as it's an Apple device, personally I have found downloading the Google app much more useful and easy to use and Safari occasionally takes longer to load and freezes.
Another problem I have discovered is that the iPhone 3GS deliberately fails to connect to the Wi-Fi in your home almost 50% of the time, personally I believe that this is a deliberate tactic Apple have used to force you to spend more money on credit to use their built-in "Ethernet" option.

Voice Control
Personally I haven't really used Voice Control much as I have no real need to, but when I have tried it out I have found that as long as you use a clear voice it will do what you require, although don't expect it to be up to the job of Siri as it's nowhere near that level!

Sustainability
My device after owning it for two years has only been left with a few miner scratches and dents much to my pleasure, although I do know quite a lot of people who also own this device and have dropped and destroyed the entire screen (although this can easily be replaced) so my advice would be if you own this device cover it because overall it is generally very sustainable, just not when dropping from a great height.

Battery Life
Depending on how bright you have the screen, the iPhone's battery can last anywhere from 2 1/2 hours to 12 hours.

Overall, although highlighting a lot of the bad points involved in owning this device, I am personally very happy with my phone and haven't yet felt the need to upgrade it at all, it's all still in working order and does exactly as I need it to do, I think it's a shame that it's been discontinued but it's still available from certain places online, so I would recommend buying it as it's now only £150-£200!