Taking out semi colons reduced the amount of redundant information needed for error recovery in the parser, leading to poorer error messages and reducing the quality of interactive IDE feedback. I know this because I was working in the IDE when martin made the decision. Maybe it was the right decision, but there were definitely costs!

There is a very good reason they will never eliminate semi colons from C#, the visual studio team would never let them...C# is developed in a completely different style from Scala.

I'm sure you are right: scala today is probably a much more simple language with great IDE support...7 years ago, it was a bunch of advanced features and building a decent IDE for it was a struggle.