I'm no developer and no OSS enthusiast (though I do like if something is OSS, but I'm not endorsing it all over the internet so...) but I use the Jolla phone since January. Why? 'Cause I love the interface. It's easy to use and once you get used to the gestures it becomes easy and fast to navigate. My previous phone, the HP Pre 3 with webOS, was also a multitasking OS and I loved it! But due to an issue that popped up after 1 year of using it (despite the fact that webOS was dead), I had to switch and so SailfishOS attracted me a lot.
I'm not dependent on much apps, a few of them are native on SailfishOS (official or unofficial) and a few of them run well under the Android runtime.

(oh and do note that I'm still very young: only 22 years old, to be exact)

Jolla is not perfect, but no company is. I don't believe in anyone or anything to be 'perfect'. Everyone and everything has flaws. But I do believe in Jolla so I support them as much as possible when they do something good or something I agree with.

So no, it's not only for devs or OSS enthusiasts. It's also for people like me who fell in love with the interface after seeing the first videos in 2013 and loving it when using it in 2014 as well.