The best looking phone on the market, the Galaxy S8, is quite susceptible to cracking so it seems. I've already seen a video of a guy who dropped the Galaxy S8 from waist height and the rear glass shattered, although didn't break. Than I saw this test done by SquareTrade Inc (see the S8 breakable test video below), and the S8 certainly looks like a quite a fragile phone, at least as far as its glass is concerned.
Some suggests that the reason why the glass cracks up relatively easily when dropped or bumped into a hard surface is because there is insufficient metal frame around the display. The metal frame should have soaked up some of the impact that the glass received and spread it across the frame to minimize the impact damage. I've seen some gadgets and laptops that implemented some silicon parts inside the phone alongside the frame to absorb that impact, and I wonder why Samsung wasn't able to implement some sort of impact protection to the Galaxy S8 to make it more resilient to impact damage.
As you can see in the video above shot by SquareTrade, the Samsung Galaxy S8's glass shattered quite horrifically when dropped from a 6 feet height. You can see the spiderwebbing breakage (at least that how SquareTrade describe it because of the shape of the cracks that look like spider's web) on the bag and star burst cracks as well. The breakage was more prominent on the back then on the front. Then they put in in a Tumble Test, which get the S8 tumble around for 60 seconds inside a rotating box with a hard surface. In that test the S8 got loose glass and spiderwebbing breakage.
Of course these are not extreme conditions, but they are a bit exaggerated. For example, a 6 feet drop (1.8 meter) is not that likely to happen and if a phone falls is probably for a lesser height, unless your are 1.90 meters tall and the phone suddenly fell out of your hand while speaking.
At the end of their test, the guys at SquareTrade Inc. gave the Galaxy S8 a breakability score of 76, which is medium to high risk. For me this means that if I buy the Samsung Galaxy S8, I would definitely buy it with some sort of protection, like a protection case or protection cover, so if it can survive a regular drop and I won't need to send it to the repair lab, which obviously will cost quite a lot of money. Repairing the S8 screen should cost quite a lot I assume.
I Googled it out to see how much a Galaxy S8 screen replacement costs and I've read that a Galaxy S8 Plus screen replacement will cost around $270 USD. This is a very expensive price to pay for a screen replacement. According to another website, The a new Galaxy S8 screen could cost you around 250 euros, which is around $270, around the same as the S8+ screen replacement price that I saw on another website. This is even more expensive than the screen replacement for the Galaxy S7 edge, which is said to cost around 200 euros. Anyways, you get the point, just make sure your S8 doesn't break.
To make sure it doesn't break you will have to buy a protection case or cover and there are plenty of them available via amazon.com. I personally would buy a scratch-resistant transparent/clear case so the S8 design still can shine through, but there are some really heavy duty cases out there that are also shockproof and provide extreme protection for your device. I would search for the full body protective cover that covers both the front and back. After all, the S8 has glass on both sides, so you need to make sure that both sides are protected.
So the S8 durability isn't that good, but not unexpected. Maybe I was a bit surprised that the Galaxy S8 glass broke so easily. The front glass is Gorilla Glass 5, so it has good degree of protection from drops, but it's not bullet proof, not at all. So this is a downside no doubt about it, but if you are like me, you will buy a case for your phone regardless.