One of the biggest smartphones of the year is going to hit store shelves tomorrow. Gizmag has gotten an early look at the Samsung Galaxy S5, and, though we'll have to wait a bit for our full review, these are our early impressions.

Update: We've now published our full review of the Galaxy S5.

The Galaxy S5 looks like a pretty subtle upgrade over the Galaxy S4, but the extras Samsung threw in definitely improve things. It's still plastic, but I think the faux leather backing feels better in hand than the standard plastic in the GS4. I've been using the HTC One (M8) as my main phone since it released, and though the One has the more premium construction of the two, the GS5 is lighter and also more comfortable to hold.

The screen is very nice, and I do notice and appreciate the extra real estate. It's 5.1 inches, next to the GS4's 5-in display. The GS5's physical and capacitive navigation keys (as opposed to onscreen virtual buttons) also guarantee that you'll always get 100 percent of that area for your apps.

This is the first time Samsung has thrown some water resistance into one of its flagships (last year you had to buy a separate version of the GS4 to get that). It seems to work as advertised, as I soaked it in a glass of water with no issues. I even used the phone while it was soaking, without any problems. One nice touch was that, when I first powered it on, the phone gave me an alert that its battery cover wasn't completely shut. Obviously that's something you'll need to take care of before taking the phone for a dunk.

The Galaxy S5 has a heart rate sensor on its back. There's no physical shortcut to start it up, so you have to fire up Samsung's S Health app before measuring (either by opening the app or tapping on a home screen widget). Once you do that, it asks you to hold your finger on the sensor for a short time (usually between 10-15 seconds) and it shows you your pulse. It doesn't seem to give you any guidance beyond showing you the results, but I suppose it isn't too hard to research where your heart rate should ideally be.

There's also a fingerprint scanner on board. Similar to the Touch ID sensor on the iPhone 5s, you teach it your print by swiping over the home button several times. After that point you can use it to unlock your phone. It recognizes mine most of the time, but I do also get annoying "swipe the entire pad" error messages if I'm not careful. My early assessment is that it isn't as good as Apple's, but is still perfectly serviceable.

I'm only just scratching the surface with the camera, but early results look pretty good. Nothing mind-blowing so far, though, and I don't think it has the low-light capabilities that you'll find in the One M8.

TouchWiz, Samsung's Android skin, is back in full force. It now follows the industry trend with a flatter design. It's almost comical to see Samsung blatantly following Apple's lead again, but I do think the new look works. Overall performance is more fluid too, with less TouchWiz lag this time around.

It's way too early to comment on battery life, or jump to any grand conclusions about how the Galaxy S5 compares to rivals. But I can say that it's a very nice high-end phone, with a look and feel that's in the same ballpark as the Galaxy S4. I don't think this is going to be a must-have upgrade – and it might not beat the One M8 in my book – but that could easily change as I spend more time with it.

Stay tuned for Gizmag's full Galaxy S5 review. In the meantime, you can hit up our HTC One (M8) review, and also see how the GS5's features and specs compare to the One, the Note 3, and the iPhone 5s.

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