UPDATE March 2014: Everything in the following article is true about iOS 7 running on the iPhone 4, but some things have changed thanks to iOS 7.1. While it's still not as fast as iOS 6 on the iPhone 4, iOS 7.1 is substantially faster on the iPhone 4. So, while those improvements might not be enough to convince you to upgrade, if you want the latest features and OS, upgrading now makes more sense.
The iPhone 4 is among the devices that Apple allows iOS 7 to be installed on. If you've got an iPhone 4, you probably already know this—you've probably been getting alerts telling you a new OS is available for download. But just because you can do something doesn't mean you should. So, the question is: If you've got an iPhone 4, should I install iOS 7?
To answer this question for yourself, you need to understand a few things about the combination of the iPhone 4 and iOS 7. For one, keep in mind that this iPhone is the oldest device that iOS 7 can be installed on. The iPhone 4 is four generations and three years old at this point, so it's far from the latest, greatest, or fastest iPhone on the market. It's got a slower processor, less memory, and a smaller battery than the newer models.
Because of this, the iPhone 4 isn't able to support all the features of iOS 7 that you'd be able to take advantage of if you were using, say, an iPhone 5S. Among the features that you won't be able to use if you have an iPhone 4 are:
- Panoramic photos
- Traffic information in Notification Center
- Filters in the Camera app
For some people, not having those features won't be a dealbreaker. For others, those are major benefits.
Should You Upgrade?
Whether or not you upgrade your iPhone 4 to iOS 7 is ultimately up to you, but I'd be cautious before doing it. If you upgrade, you'll be putting the latest OS, which requires a lot of processing horsepower and memory, onto a device that's coming close to the end of its usable life. The combination will work, but it may be slower or more problematic than you'd like.
If you're willing to live with some bugs or slowness and just have to have the latest OS, go for it. Otherwise, I'd consider holding off.
But does that mean you can't use iOS 7? Not necessarily.
A Better Upgrade
If your current phone is an iPhone 4, you probably bought it more than two years ago. Most cell phone companies offer their customers a discounted upgrade every two years, meaning that you could get an iPhone 5S or 5C at their lowest advertised prices (US$99-$399) as long as you sign a new contract with your provider.
This is the best of both worlds: you'll get a fresh, fast new phone with all the latest hardware features, and iOS 7 will come pre-installed on it. I'd much rather pay $99 for all those new things than have a poor experience on my old phone.