While smartphones based on Google's Android operating system collectively outsell Apple's iPhone, no single Android phone has risen to become a giant hit the way the iPhone has. Instead, there has been a profusion of often-confusing models with mostly forgettable names and design tweaks dictated by mobile carriers.

Now, Samsung, the leader in Android smartphones, is aiming to change that. It is rolling out a single new flagship model, with the same design and features, on all four major U.S. wireless carriers this month and next.

I've been testing this new phone, the Samsung Galaxy S III, for several days, using variants for Sprint, T-Mobile and AT&T. The phones, which come in white and a dark blue, are indistinguishable externally except for the carriers' names printed on the rear. Inside, they are also identical, except for the technical underpinnings needed to work on the different networks, and some app icons preloaded by each carrier.

Like other new Android phones, this Galaxy S sports a huge screen -- 4.8 inches -- and an 8 megapixel rear camera. But it's thinner and lighter than the iPhone 4S, even though the latter has a 3.5-inch screen. So the Samsung feels a bit smaller than it is. Prices will start at $200 with a two-year contract. The phone runs the latest version of Android, called Ice Cream Sandwich.

Based on my tests, I consider the Galaxy S III a very good phone, and a strong competitor for the iPhone and for other leading Android models. In every major feature area, such as voice calling, Web browsing, and photography, it performed very well. I can recommend it to people who would like a much bigger screen than Apple offers, who prefer Android, or who are attracted by some of its secondary features, like new ways of sharing content.

However, the Galaxy S III lacks any game-changing capabilities and is instead packed with a dizzying array of minor new tricks that users will turn to frequently. There are so many of these that it can take hours to learn and configure them. I had the strong impression Samsung's designers failed to focus and just threw in as many technical twists as they could, some of which didn't work very well.

One feature that Samsung touts lets you share, in real time, photos you take at an event -- like a party. It sounds cool, but it only functions with friends who also have the Galaxy S III. And all participants have to go into settings, turn on a special kind of Wi-Fi and then tap on a series of on-screen buttons, a process that kind of drains the spontaneity.

The first carriers to offer the phone will be T-Mobile and Sprint, followed by AT&T, and then, early next month, Verizon Wireless. Sprint, Verizon and AT&T are selling the 16-gigabyte model for $200 with a two-year contract, but T-Mobile is selling it starting at $280, after a $50 rebate, if you buy its most common 'classic' data plan. Service plans are similar to those on other smartphones. A pricier 32-GB model is available, except at AT&T.

One concern about any Android phone is whether it can be upgraded to the coming versions of the operating system. Unlike Apple, Google doesn't control this -- handset makers and carriers do. And only a small percentage of Android phones currently run the latest version. Samsung couldn't assure me the Galaxy S III would be able to work with the next couple of versions of Android, since it hasn't tested them yet on the device. But it said it left extra memory inside to fit a larger OS.

On the major criteria, the Galaxy S III is mostly a winner. The screen is sharp and vivid, avoiding the over-saturation I've seen on some other recent Samsung devices. The sound is good, and the on-screen keyboard and dictation worked as expected.

Voice calls on all three phones were clear and didn't drop. Data speeds varied by network. In the Washington, D.C., suburbs, I got about 13 megabits per second download speeds on the AT&T and T-Mobile versions, and much less on the Sprint version.

The camera worked well and has nice features, like a 'best photo' mode, which quickly fires eight times, then suggests the series' best shot. When recording video, you can simultaneously take a still picture.

My only big concern was battery life. I didn't do a formal test, but all three phones had only about half of their batterycapacity left by midday, despite a feature that supposedly can detect your eyes looking at the screen and keep it bright only when you're doing so.

Then there are the secondary features. You can broadcast a presentation or photos to groups of devices that use Samsung's sharing software, bump two Galaxy S III phones together to transfer content and do other things to share files. I tested them all and most worked only some of the time and took some setup.

You can also dial someone with whom you're texting simply by bringing the phone to your ear. This worked for me, but not always.

Finally, Samsung has its own version of Siri -- the voice-controlled assistant on the iPhone -- called S Voice. In fact, it does more than Siri. It can launch apps and turn Wi-Fi on or off. Like Siri, it doesn't always work.

The Galaxy S III is a solid, capable phone. But its most important feature may be ubiquity.