As always: it depends.
As a peripheral observer and user of Scala, I feel like it gets a lot of things right if you want to use it as a "better Java". But that doesn't mean it's particularly usable as a "better Java"; obviously reasonable people can disagree but personally I find it uncomfortable to write Scala code for too long. It feels like it leads to awkward structures (blocks within blocks within blocks, hard-to-follow but oh-so-functional transforms) and an odd sort of terseness that reminds me of Python (not a compliment, I find Python irritating to read even though I like a lot of the ways it does stuff). It's like there's so much stuff there that it encourages you to be way too clever. "Too clever" is a thing and a bad one; somebody (maybe even you) has to puzzle out your cleverness later.
I do find cases where the language actually does cause problems, though. There appears to be three main groups involved with Scala: PL academics, "better Java" people, and "why isn't it Haskell?" people. The last group is, to me, rather frustrating, because it's the group that gets up in arms at the idea of a 'for' statement in the language. (The standard method of iteration is a foreach method over a collection and it is insanely slow; people resort to writing while loops because the foreach construct is so laughably slow. Why am I faking a for loop in such a "modern" language?) There are a few areas like this where practicality has apparently lost out to zealotry and it makes the language feel vaguely hostile to somebody who already Does The Right Thing in Java (immutable-by-default, dependency injection rather than creation, etc. etc.). As silly as it may sound, when I'm writing Scala I don't feel welcome in my own code--and I've been using Scala off and on for a couple of years, it's not just fear of the unknown.
I'm actually really looking forward to Kotlin (and Ceylon, to a lesser extent) because it's a language with a focus. JetBrains knows where they want to go with it instead of just dumping a box of stuff on your lawn and telling you to piece together what might or might not actually be what you want. The comparison always reminds me of The Big Lebowski: "Say what you want about the tenets of National Socialism, dude, but at least it's an ethos!"
As a peripheral observer and user of Scala, I feel like it gets a lot of things right if you want to use it as a "better Java". But that doesn't mean it's particularly usable as a "better Java"; obviously reasonable people can disagree but personally I find it uncomfortable to write Scala code for too long. It feels like it leads to awkward structures (blocks within blocks within blocks, hard-to-follow but oh-so-functional transforms) and an odd sort of terseness that reminds me of Python (not a compliment, I find Python irritating to read even though I like a lot of the ways it does stuff). It's like there's so much stuff there that it encourages you to be way too clever. "Too clever" is a thing and a bad one; somebody (maybe even you) has to puzzle out your cleverness later.
I do find cases where the language actually does cause problems, though. There appears to be three main groups involved with Scala: PL academics, "better Java" people, and "why isn't it Haskell?" people. The last group is, to me, rather frustrating, because it's the group that gets up in arms at the idea of a 'for' statement in the language. (The standard method of iteration is a foreach method over a collection and it is insanely slow; people resort to writing while loops because the foreach construct is so laughably slow. Why am I faking a for loop in such a "modern" language?) There are a few areas like this where practicality has apparently lost out to zealotry and it makes the language feel vaguely hostile to somebody who already Does The Right Thing in Java (immutable-by-default, dependency injection rather than creation, etc. etc.). As silly as it may sound, when I'm writing Scala I don't feel welcome in my own code--and I've been using Scala off and on for a couple of years, it's not just fear of the unknown.
I'm actually really looking forward to Kotlin (and Ceylon, to a lesser extent) because it's a language with a focus. JetBrains knows where they want to go with it instead of just dumping a box of stuff on your lawn and telling you to piece together what might or might not actually be what you want. The comparison always reminds me of The Big Lebowski: "Say what you want about the tenets of National Socialism, dude, but at least it's an ethos!"