Ever since the launch of the first iPhone in 2007, Apple (AAPL) has introduced one new model a year. Now, for the first time, there are two: the new flagship iPhone 5s, and the lower-cost, colorful iPhone 5c, both of which arrive in stores Sept. 20. After a week of using them, my view is simple: If you like Apple products, you’ll like these; if you don’t, you won’t. With its ease of use, enormous wealth of high-quality apps and content and well-integrated online services, the iPhone still provides the best overall user experience of any smartphone. But while Apple has never introduced this many iPhones, it’s also never changed so little from the previous generation.