A buyer's guide to the new iPhone 4S

Apple is trotting out a new iPhone on Oct. 14, but it's not the iPhone 5 some were expecting. Instead, it's a more modest upgrade, the iPhone 4S . Here are some facts to help you decide if it's time to make the plunge.

- If you own an iPhone 4: The new phone will have a faster processor and a sharper, more responsive camera. Otherwise, it's pretty much the same. It will come with improved software, but you'll get that as a free update on your iPhone 4, too.

As an iPhone 4 owner, you should consider the 4S only if you absolutely must have the latest and greatest, or if your old phone is broken. Since the 4S is less than two years old, your carrier will probably make you pay more than the $199 base price if you upgrade, because you haven't "paid off" the subsidized price of your old phone yet.

There's speculation that the more significant iPhone 5 upgrade may be less than a year away, and it could add important new features that are worth waiting for.

- If you own an older iPhone: Apple's new software, iOS 5, will work on the iPhone 3GS, but not the original iPhone or 3G. Take the launch of the iPhone 4S as a good opportunity to upgrade to a faster, more responsive phone, with a sharper screen.

The big cost of owning an iPhone isn't in the purchase price, it's in your monthly service fees. Upgrading your phone every two years is a minor cost compared to paying your monthly bill over the same period. So take advantage of your carrier's phone subsidy and let it treat you to a new iPhone. Because Apple charges about $600 for a phone that costs $199 in the store, it's the phone company that eats most of the upfront cost of the phone.

- If you don't have a smartphone: iPhones are still the kings of the smartphone world, with unsurpassed access to high-quality applications. But they're also expensive. That may not be immediately obvious in the cellphone store, where their $199 price tag (or, in the case of the iPhone 3GS, $0 price tag) looks comparable to many other phones. Carriers require contracts when selling iPhones at that price, and the available plans aren't cheap, in part because you'll need a data plan. In effect, you'll be paying off that expensive phone over two years, through your monthly bill.