I agree that "+" looks better than ".plus" but this is a matter of taste (hello Ada).
Yes, I use Scala at work but I can't call myself a seasoned Scala dev, true. On the other hand, just every expert in this or that language will always have a counterargument for you and a solution to the problem. Because he IS an expert! The thing is, not all people are experts or even will be. Most people want a tool that doesn't get in your way, easy to pick up and deliver the results. That is why Python is so popular despite being slow, inefficient and basically a glue for C/C++ libraries. Hell, even for interfacing with C Python loses to Lua. But all these shortcomings didn't matter in the end. Python2 → Python3 didn't kill the language either. I am afraid Scala's error margin is not as big.