Nevertheless, I took a glance on Scala few months ago, and I have found it very interesting, concise, agile, and efficient. The learning curve is also quick to learn. Another point is the ability to mix java and scala, and the most important is the disponibility of an eclipse plugin for developping efficiently... So why not using Scala as well?
An interesting article from James Strachan, the creator of Groovy about Scala. At the beginning, I was quite fan of Groovy, but personnaly I think syntax and concepts have evolved in a too complex manner... even if Groovy has powerful features which may match some areas like specific domain languages or metaprogramming.