Only problem is that it's not sound. That means that while it may provide static checking that your program is validly linked together, it can't fully prevent run-time type errors. And kind of like you can't be "a little pregnant", you can't be "a little typesafe".

Of course you can. Can't catch all the bugs; but can catch some of them. Which saves time and money. It doesn't actually have to be perfect to be useful and helpful.

I'm not saying it doesn't help. I'm saying you can't count on it the same way you can if you're working in a truly end-to-end statically typed environment. Even Scala's type system has its leaks, due to nulls.