I've been mountain biking for about a decade and started as a transition away from BMX. so a singlespeed mountain bike always made sense to me.
currently on a Karate Monkey with a dropper post, 120mm suspension fork, and one gear. I've been playing around with combos and found that 50 gear-inches is great for smoother terrain but it forces me to walk a LOT in the chunk. that's a 34/20 combo with 29" tires. I tried 32/20 but it forces me to push my axle back further than I'd like and it's kind of the worst of both words: too spinny on the flat and not low enough to climb through chunk. I switched again to 32/21 and that seems just right. yup, it's slow on the road and I don't care. that's worth the trade-ff that comes with being a little more capable of clambering over the chunky stuff to me. when I finish a ride, I don't care how fast I went, I care about how much I was able to ride instead of walk.
I don't have to talk about "my singlespeed" because each of the two bikes I own are both SS.