Of course they are, but thé article seems to be from someone interested by elixir, rather than someone who used it long enough to discover them (although I might have misunderstood the article.)
From own experience, the problematic parts are :
- deployment being a bit messy if you try to follow 12 factors (might be improving in 1.9)
- absence of a decent debugger
- younth of the ecosystem and size of the community (aka hard the find a maintained lib that works for a few common issues.)
- compiler being a bit slow to my taste (YMMV)
- then, of course, the elephant in the room: the absence of the kind of static type checking that facilitate refactoring ord relatively large codebases.
Nothing unbearable or permanent, but some things to keep in mind. Go try it !