Philosophical matters aside, the Galaxy S4's capacitive keys are frequently not lit up during use and thus impossible to see. And the mix of physical and capacitive buttons creates an awkward usage scenario that's anything but ideal: As I noted when reviewing the Galaxy S III, once you get used to gently touching the capacitive buttons to activate them, having to forcefully press the adjacent physical home button is jarring.
Sounds like a lot of nitpicking, I know -- but all it takes is 10 minutes with a device that follows Google's Android 4.x-level design guidelines to see how big of a difference these seemingly small details make in the overall user experience.
Under the hood
The U.S. model of Samsung's Galaxy S4 runs on a cutting-edge Qualcomm Snapdragon 600 1.9GHz quad-core processor along with 2GB of RAM. With that sort of horsepower, I've been surprised to see that the phone's performance suffers from subtle but noticeable hiccups.
The GS4's system animations are frequently jerky, for instance -- like when the phone is returning from an app to the home screen -- and some actions take far longer than they should to process. I've counted as many as eight to nine seconds after tapping a folder in the Gallery before it actually opens. And these things haven't been isolated, one-time occurrences; they've happened regularly, regardless of what other services the phone has been running or how much time has passed since a restart.
What's most baffling is the fact that the HTC One, which I found to have near-flawless performance, uses the same exact processor -- clocked slightly lower, in fact -- and the same amount of RAM as well. The only logical conclusion I can draw is that something having to do with Samsung's software is gumming up the works.
To be clear, the Galaxy S4's performance isn't all bad -- for the most part, apps usually load quickly, Web browsing is swift and smooth and the system doesn't feel terribly sluggish -- but for a flagship phone with this level of hardware, any amount of jerky or lag-laden performance is disappointing.
The Galaxy S4 does do well when it comes to stamina: The phone packs a removable 2,600mAh battery that's generally provided ample juice to get me through the day. Results will obviously vary based on what you're doing, but with a few short voice calls combined with scattered Web browsing, social media activity, camera use, audio streaming and the occasional video streaming (about 2.5 to 3 hours of total on-screen time), I've found I can usually squeeze in around 13 to 14 hours of use before the phone starts giving me low battery warnings.