Here's what experts are saying about it:
Andrew Chun, analyst at IM Investment and Securities, Seoul
"It's somewhat disappointing. If you just look at key features, some are new but most of them are not really differentiating ones compared with what rivals have already unveiled.
"The S4 has a bigger screen so it could attract consumers preferring larger display, taking them away from Apple. Competition will only get tougher as prices go down but Samsung will be able to increase shipments through an intensive marketing campaign."
Lee Sun-Tae, analyst at NH Investment and Securities, Seoul
"Key hardware features somewhat failed to meet hyped-up expectations and there's no hardware feature with a "wow" factor that many had expected. But I think the product is still ahead of its rival devices and this is good enough to win market share in the high-end segment. The other thing worth taking a note here is Samsung is now targeting enterprise clients and BlackBerry customers by adding Knox security solutions."
Brian Marshall, analyst at ISI
"The S4 possesses all the relevant new features for an industry-leading product. Most importantly, it features a large canvas (that is, the 5-inch AMOLED display), which we believe is critical as users look to converge smartphone and tablet functionality into one device.
"If the Galaxy S4 ran the (Apple) iOS platform and had Apple's ecosystem attached to it, it would likely be the world's ultimate smartphone.
"Despite Samsung's success, we believe Apple is not standing still and our view is unchanged that the roughly 2 billion-unit cellphone market is large enough for several vendors to flourish."
Charles Golvin, analyst at Forrester
"It looks like a great flagship device to me. Assuming they get very broad availability across geographies and carriers, and the price is on par with competition, then I think they will sell quite a few of them.
"It's significantly forward from the S3. There are a lot of new features, some new hardware features that are noteworthy, like the IR (infrared) gesture capability, some of the environmental sensors they mentioned, like the barometer.
"What is really noteworthy is Samsung's investment in software and the development of the software features. That's where the real differentiation and payoff comes from. What really struck me were these innovative software features, whether it's the real-time compositing of images or hovering over the screen to do all kinds of different controls, these software features were what were really impressive to me.
"It holds up very, very well (against the iPhone 5). There are lots of things that are in there that the iPhone doesn't have. People who like larger displays will see this as a better phone than the iPhone.
"There's a lot you can do with this phone with the range of applications in the appstore that you can't yet do on the iPhone. Samsung has fulfilled the promise of their marketing that they are the tech innovators. It remains to be seen whether it's overload for customers, whether they can really take advantage of all these features."
Mark McKechnie, analyst at Evercore
"It sounds like its a pretty major launch in terms of the scale of carriers," numbering 327 in 155 countries.
"Its kind of incremental. I didn't see it as a dramatic change.
"Its hard to say whether that'll be seen as gimicky, or if it'll be a major selling feature.
"The product feels good."
Jan Dawson, chief telecom analyst at Ovum, New York
"The Galaxy S4 is a worthy successor to earlier members of this line, and will doubtless sell well. But it highlights a couple of the key challenges Samsung faces. Firstly, having innovated rapidly over the last several years to vaunt itself into top spot in the world smartphone rankings, Samsung now faces essentially the same challenge as Apple: how to continue to improve its devices year on year when existing phones are already top of their class, and there aren't obvious shortcomings?
"At this point, Samsung appears to be trying to kill the competition with sheer volume of new features - there should be something here for everyone, even if most of these new features won't be used by most users.
"For now, Samsung can likely rely on its vastly superior marketing budget and the relatively weak efforts of its competitors in software to keep it ahead. But competitors will catch up and Samsung will need to continue to stretch.
"Overall, there are lots of features, but based on past experience most people will never even find them on the device."
Copyright @ Thomson Reuters 2013