I think the bigger hurdle to Scala adoption isn't language complexity, but tooling. It's not as mature as Java tooling, and compilation is dreadfully slow. Typesafe is actually putting some effort in improving Scala tooling, so hopefully the additional funding will help them move the ball faster in that area.
Yes! Exactly. This is the problem, not Scala being complex.
Fortunately they are improving fast. FSC support in Idea is pretty good. If you have a decent processor, compilation is no longer an issue.
Scala is really very easy to start for someone who knows mainstream languages like C++ or Java or C# - you just start writing in it like in a better Java, then slowly learn new concepts... For me it took two weeks to feel comfortable with it. Actually much faster than with Python.
Yeah, this is ultimately what prevents me from contemplating using Scala in a broader context. I will admit I haven't tried for a while, but every time I've tried out the Scala eclipse plugin it's been incredibly flaky. For the top tier of developers this doesn't matter too much (they can either handle flakiness or do without an IDE at all) but companies specifically do not want to build their systems dependent on constantly having top tier developers to do every little change they need.
You can contrast with Groovy which while still not perfect, has an awesome eclipse plugin and SpringSource offers a whole customised eclipse version for working with their stuff.
