In every measurable way the phone is an improvement on its predecessor, the S3. It's slightly thinner, lighter and faster, squeezing a few more megapixels into the camera and twice as many dots into the screen.
Externally there is very little to choose between the two models. Much like Apple's progression from iPhone 3G to 3GS and then iPhone 4 to 4S, the Galaxy S4 feels like mid-season upgrade; a higher-spec S3 rather than an all-new model.
It's in the phone's software, however, that Samsung has made the biggest leaps forward. New camera modes allow for multiple-exposure action shots, automatic photo albums and a neat trick mode that combines the front and rear-facing cameras, allowing the photographer to appear in the same shot as their subject.
An eye-tracking feature automatically pauses video clips when the viewer looks away, resuming playback when the their gaze returns to the screen, while a related feature allows web pages to be scrolled simply by waving a hand over the screen.
Both ideas sound clever in principle, but in practice the implementation is too flaky to be fun. Touch the screen and it'll scroll as quickly and smoothly as any other high-end Android phone, but attempt a mid-air swipe gesture and the phone will decide an action seemingly at random. It may scroll up, navigate back a page, or it may dial the local pizza shop. Likewise, the video auto-pause feature is a hit-and-miss affair.
I was also unconvinced by Samsung's new Group Play feature, which allows up to eight Galaxy handsets to be used as speakers in a surround sound system. Friends can wirelessly bond their phones together to create an ad-hoc ghetto blaster.
The audiophile within me dislikes the result (simply louder tinny rubbish) while my inner grumpy old man fears for public transport as groups of teenagers seek to fill entire train carriages with Justin Bieber. It's also a fact that the best loudspeaker solutions are designed for iPhone only.
New Samsung accessories help the S4 bridge the gap to the iPhone. The S Band – a wrist-mounted activity tracker – offers similar features to Nike's iPhone-only Fuelband while Samsung-branded bathroom scales and a heart-rate monitor replicate the features of other third-party, iPhone-only gadgets.
With the improvements in the Galaxy S4 it looks like Samsung's place at the top of the Android charts is assured for another year. Whether the S4 can help Samsung take a bigger slice of Apple's market share remains to be seen.
Positives The world's most popular Android phone just got better.
Negatives New, cutting-edge features lack polish.