However, we find these days that many of the stereo systems use AirPlay rather than plugging in directly, and we don't really miss our old iPhone accessories.
In terms of iOS 8, bear in mind that the iPhone 4s misses out on some of the showier improvements.
iPhone 4 (currently not on sale)
The iPhone 4 looks very similar to the iPhone 4s, and like that model it uses a Micro-SIM. The key difference is the number of megapixels offered by the camera: 5Mp in the iPhone 4 compared to 8Mp in the iPhone 4s. It launched in June 2010. Read our iPhone 4 review.
iPhone buying guide: iPhone 4
If you've got an iPhone 4... If you're still using an iPhone 4 then now is a good time to upgrade. Whichever of the four currently available iPhones you choose will add a bigger screen, thinner chassis and 4G capabilities. The iPhone 4 is well behind both 4S and 5 in its photographic fidelity and has no Siri voice assistant. It's also about a quarter as fast as the iPhone 5 so imagine how much faster the new iPhone 6 will be.
In terms of iOS 8, bear in mind that the iPhone 4 will not be supported so you will be left behind in terms of new features and other improvements that will come with the new operating system — including new features coming in Mac OS X Yosemite that will make your Mac, iPhone and iPad work together.
iPhone 3Gs (currently not on sale)
The iPhone 3Gs was the last of Apple's plastic iPhones for several years (the company eventually returned to plastic shells for the iPhone 5c). It had a 3Mp rear-facing camera but no front-facing camera for FaceTime. Like the 3G, this model came in black or white. It launched in June 2009. Read our iPhone 3GS UK review.
If you've got an iPhone 3GS (or an earlier iPhone model)... A lot of people are still happily using an iPhone 3GS. Perhaps they adopted one when a family member updated their iPhone. They have missed out on iOS 7 and more recently missed out again on iOS 8, so for the sake of new software features alone it may be time to update.
There's no need to jump right up to the iPhone 6 in this case, of course. The cheaper iPhone 5c may well suit you, and you could probably pick one up for a good price on eBay or similar.
Whatever you update to, you will enjoy a Retina display, a marvel of touchscreen technology with pixels so closely packed they can fool the human eye, and a far cry from the 3GS.
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