Have you ever heard of immersive mode? It's a new feature in KitKat that allows apps to go fullscreen, thus allowing the M8 to use all 5 inches of its display. More and more apps support immersive mode every day.
There are launchers with immersive mode...
http://www.movemarketing.co.th/wp-content/uploads/2014/01/google-nexus-5.jpg
Google Now / Search has immersive mode...
http://cdn.androidpolice.com/wp-content/uploads/2014/02/nexusae0_2014-1.png
There are reading apps with immersive mode...
http://i0.wp.com/c2.bgr.com/2014/03/android-kitkat-immersive-mode.jpg?w=625
There are gallery apps with immersive mode...
https://lh3.ggpht.com/EKEX5Ftx-h1kjihunlVTXznG_kvzmWQt-jl9AOY00PiV5X0bLNAK9abKm3ZZAzDb9X3-=h900-rw
There are twitter apps with immersive mode...
https://lh4.ggpht.com/qEzAAzdR0FHcb43_6PCk7zcfVwHEefUreHmOtrWNyO3jF2ezeW0odzEYcc42N9tv7g=h900-rw
There are texting apps with immersive mode...
https://lh3.ggpht.com/sl5PbkxwoN6_oyWutrbl7O86D81ScaBU_Q5t39akaWhg4pSL6mLt0vn0ol0YniZ_xgk=h900-rw
There are lockscreen apps with immersive mode...
https://lh4.ggpht.com/sJs4ikSpE1c56RMqJGEI_s8uV2Ld-QtPu3UsJWpL4988zOELStYsPL21WJCtnVIxTTyP=h900-rw
There are file explorers with immersive mode...
https://lh6.ggpht.com/NtRxFz4CXK21vOEeBnt_gJHrHJH-rAilPaaWFFf1nBqjKT9wDXPw6ABypwLFUd3smg=h900-rw
There are RSS readers with immersive mode...
https://forums.androidcentral.com/e...id=com.twentyfivesquares.press&token=0jdCm_gI
Heck, immersive mode is even coming to Chrome browser. You can enable it in the beta version now.
Not to mention, every video playback app and most games out there support immersive mode already.
So you can certainly make use of the extra screen real estate on the M8 a lot of the time, and it will only be easier to make use of it going forward as more apps add support for immersive mode.