Apple began shipping the iPhone 4 at the end of June, and the price of the entry-level 8 GB iPhone 3GS was recently slashed to $49. The new model’s biggest change is its Retina display, which has twice the resolution of previous iPhone screens. The result is that you can’t see individual pixels unless you use it much closer to your eyes than usual. The iPhone 4 is also the first iPhone designed around a multitasking version of the iPhone OS, iOS 4.