However, most languages in common use are not "modern" by this definition (if by any) ;) I've switched from C# to Java and the clunkiness of it drives me crazy. I know that Java 8 brought a new LINQ-like API, but it won't be available for Android development for a while (not to mention there's existing codebase to maintain etc.).
This is very true -- most languages in common use are 20 or more years old and were not cutting edge when they were created. However you don't have to accept the status quo. Scala is viable on the JVM, F# on .Net, and Haskell (and increasingly Rust) if you want to avoid a VM.
C# has enough functional capabilities (for typical development needs like mine), so I never felt the need of using F#. Scala, on the other hand, looked quite neat.
The problem with Java 8 on Android is JDK 7, as it introduced invokeDynamic that will have to be supported by Dalvik, plus I think the additions to the standard library are also a work in progress. It will happen though.
For Android you can use Scala and many people do it. There's a SBT plugin for painless setup and you can work with IntelliJ IDEA as your IDE. Some people even go for Clojure. For iOS, there's RoboVM [1] and you can also use that in combination with Scala - it's very promising.
Java the language sucks, but the JVM and the ecosystem are great and you've got mature languages designed to run on top of it, languages with big communities behind them. Of course, learning a new language and finding the best stuff in a huge ecosystem where choices abound takes time and patience, but I think you'll learn to appreciate it - or if you like C# so much, there's always Xamarin, though it's a little pricey.
If I was an entrepreneur, I might, but as an individual developer, I couldn't afford it...
It's a real pity that Google didn't go with C# as their language of choice for Android development. The world would suck less. And they actually considered it...
"If Sun doesn't want to work with us, we have two options: 1) Abandon our work and adopt MSFT CLR VM and C# language - or - 2) Do Java anyway and defend our decision, perhaps making enemies along the way"
