Having Typesafe should make it easier for companies to use Scala more and right now that is one of the very valid points against Scala, it simply isn't used as much out in the market place as other options. I truly expect that to change with time and I see this being a step in that direction. It will also make it easier for our sys-admins to get everything set up nicely and that is a big plus.
The number of additions in Scala 2.9 is significant. You can read all about them on the Scala site, but I want to highlight the ones that I think will be good for my teaching. The first one is the additions to the REPL. The REPL is a great teaching tool. It truly allows the student to get started typing in single statements and then to keep playing around with things later on to see how they work. Through 2.8 the REPL in Scala had some rough spots. The list of fixes for 2.9 seems to cover most of the problems I've run into so I'm very hopeful that the students next semester will have a much better experience with it.
The key addition for most developers in 2.9 is parallel collections. These will impact the second semester and beyond because I introduce parallelism in the second semester. Early on, this makes it easier to to parallel loops in Scala than it would be with even OpenMP. Consider this code that calculates and prints Fibonacci numbers.
for(i <- 0 to 15 par) println(fib(30-i))
When you run this using the slower, recursive version of fib, you get the numbers back out of order with the biggest values near the end. Just adding the call to par is all it takes. Of course, the for loop and collections can do a whole lot more than this and they will also do their tasks with the simple addition of a call to the par method.
Not only did the collections get parallel, they got a new set of methods that come standard: collectFirst, maxBy, minBy, span, inits, tails, permutations, combinations, subsets. These just make the already rich set of methods on collections a bit richer. The last three, in particular, strike me as easily enabling some interesting problems.
The last addition I want to highlight is one that I really don't know all that much about and as such I'm not certain how much it will impact my teaching. However, I'm optimistic about it. This is the addition of the scala.sys and scala.sys.process packages. I use the scripting environment of Scala in the first semester. I love how this lets us write programs with a low overhead. Up to now though, Scala hasn't really been good for scripting in the sense of launching lots of processes and dealing with the OS. These packages look like they will help to bridge that so that I can use Scala for those types of things instead of having to move to the ugliness that is Perl.