I don't understand why anyone would complain -- maybe I'm just lucky but I don't have the defects that others had -- same thing with my M7 (although it developed the purple Camera tint -- now that I have my M8, I can have it replaced).
I owned a Galaxy S5 for about 3 weeks before I got my M8 (my supplier's fault: he took forever to get me one). Not impressed with the S5. It always felt cheap in hand and while the camera and screen were great, I could never get over how flimsy it felt. Honestly, my logitech G700s mouse feels sturdier in comparison.
Meanwhile, the build quality and materials used in the M8 -- as well as the ongoing refinement of Sense -- puts it far ahead of anything Samsung, Sony (comes closest), LG or any of the others have.
Regarding Sense -- do any of you realize that Samsung's stock dialer on the S5 is nearly the same thing it had on the Galaxy S2 but with slightly different colors? It's crazy -- Gingerbread design in a KitKat world. Also, the fingerprint scanner on the S5 is a joke -- I own an iPhone 5s and I'm shocked that Samsung bothered to ship a phone with such crappy fingerprint recognition just to "compete" with Apple -- and it's not like TouchID is perfect. Regardless, pitting their fingerprint scanners head-to-head was like pitting a kindergarten kid (Samsung) against Lebron James (Apple) in a game of basketball. It's a travesty.
Also, I've seen numerous reviews comparing the S5 and the M8 and 9/10 were all in favor of the M8. One exception was GSM Arena (quite possibly paid off by Samsung), which actually claimed TouchWiz was better than Sense. I laughed so hard at that one. GSM Arena has been shilling for Samsung since at least the Omnia days; I stupidly bought one back then because I believed its review.
With respect to the Camera -- by now, consumers are sophisticated enough to know that the camera megapixel count isn't that big of a deal given the use cases for most camera phones -- I can't even remember the last time I transferred a phone camera photo to my PC. If I want to go nature-hiking and take photos, I have a DSLR for that.
To conclude, owning the S5 always felt like owning the 2nd-best thing out there. Now that I have my M8, I feel like I own the best Android device available.