The tooling argument can go both ways. For instance Visual Studio + Resharper is much much better than any option for Java. The Java profilers are nearly useless when compared to something like Red Gate and the integration with Sql Server on the MS stack makes database programming much easier.

The Microsoft build ecology is a little bit more mixed bag, but when compared to the explosion of choices for Java between Ant/Maven/Ivy etc. I'm not sure which I prefer.

As far as languages, working in C# makes working in Java so painful. C# makes so many better language/library decisions. The problem is that the JVM is a very compelling target platform (much more so than being stuck on Windows).

With those constraints Scala is a very nice language to use. In fact I dread every minute I have to spend in Java. Further everyone I know personally who has spent time in Scala feels the same way. I've literally never met anyone in person who prefers Java to either C# or Scala from a language point of view.

IDE for Scala sucks, mostly because Java developers are spoiled with Intelij IDEA and, to some degrees, Eclipse. It is still very usable. If you don't care about IDE, that is a non-issue.

What other Scala tools you're referring to? Scala can reuse almost all popular Java tools.

Also, can you elaborate on strict coding convention? do you mean operator overloading?

The IntelliJ Scala plugin is actually very good. We didn't have any strict conventions, just code reviews and good taste. Our devs didn't have any major trouble, but your experience may be different.