I first saw the back in February when it debuted at the Mobile World Congress in Barcelona. The phone launched shortly afterward in Europe and South Korea, where consumers bought 5 million smartphones in 85 days, making the Galaxy S II the fastest-selling Samsung phone ever.

I received a of the European version in May, and was impressed with the Galaxy S II's superthin design, gorgeous display, and fast performance. All of the Galaxy S II phones use Samsung's Super AMOLED Plus display technology, which we first saw at CES on phones such as the Droid Charge and the Inspire 4G. According to Samsung, Super AMOLED Plus displays have 50 percent more subpixels than first-generation Super AMOLED displays do. In my hands-on review, I noted that colors looked bright, details seemed crisp, and the viewing angles were very good. Blacks looked deep, and colors appeared richly saturated without being overdone. Even when I held the Galaxy S II in direct sunlight, its display Samsung Galaxy S II for Sprintremained incredibly visible.

All of the phones ship with Android 2.3 (Gingerbread) as well as a new version of Samsung's TouchWiz user interface. The revamped TouchWiz 4.0 is fairly similar to the previous version, but it has a few aesthetic and functional enhancements here and there. For instance, the new lock screen displays missed calls and unread text messages; you can swipe these notifications rather than having to unlock your phone and then dig through menus to find the missed messages. The Galaxy S II's keyboard isn't the native Android one, but it retains the multitouch key-chording feature (you can simultaneously press Shift and a letter to produce a symbol or number--no need to switch between modes) and the ability to use your voice to correct words as you type.

All of the Galaxy S II phones have six-axis motion sensing, powered by an accelerometer and gyroscope. This feature is great for gaming, but Samsung also throws in some gesture-based controls for the phones. For example, you can zoom in and out of images in your gallery or in the browser by tilting the phone. It's a neat idea, but when I tried the function out on the European Galaxy S II, it felt a bit awkward.

Like all Galaxy phones, the S II provides Samsung's Media Hub for your movie- and TV-watching pleasure. In my tests, video looked fantastic on the handset's display and played back smoothly. Even if you don't like Media Hub, you'll want to watch a lot of movies and TV shows on one of these phones because the display is so fantastic.