When I first encountered Scala, my impression was that this would be Java 2.0. Two plus years later, that's still my impression. What this means to me is that if you are looking for a new work-a-day language (i.e. the language that you use to pay the bills; the ones that appear in the Tiobe top 25), then Scala is probably worth a look. However, if you are happy with your current working language and are, instead, loo…
However it is not correct to say that Haskell is more expressive than Scala. It is in some ways but Scala is more expressive in others. There is a paper that discusses type classes in Scala and show they have some advantages over Haskell's implementation. As more people use Scala and discover neat things you do in it, this is feeding back into other languages. For example, here's the mighty Oleg implementing the cake pattern from Scala in Haskell: http://okmij.org/ftp/Haskell/ScalaCake.hs