I work for a company that has several parts of a larger product
written in Scala (mainly because it was just simpler to write it in
Scala). We have zero issues, apart from some problems related to
boxing that we soon fixed. Additionally, about 80% of the test code
has now been ported to Scala (this is a great way to introduce the
language).
Please note that even though Scala runs on the JVM, it is not really a
better Java. It's much, much more and if you are willing to learn, the
language will keep surprising you (mostly in a good way - inline type
annotations notwithstanding).
You can start using Scala like Java, but you will start to write more
functionally with time.
You may experience any issues as you would experience with Scala - its
takes some learning but you soon get used to it.
Regards,
Gary
The test libraries available for scala are very, very good. ScalaTest,
Spec2 etc are fantastic in general but ScalaCheck is truly amazing.
Regards,
Gary