Value types would help quite a bit performance wise for tuples and case classes. Escape analysis helps reduce heap allocations of such objects a bit, but at the moment the JVM can't inline some method calls aggressively enough thus can't eliminate heap allocations for these small immutable objects. This leads to heap trashing and 3-4x higher execution time.
Value types also helps increase data locality and reduce memory usage. For example, in a simple Array[(Int, Int)] each array entry will have an overhead of one pointer + object header. With value types this overhead could be eliminated completely.
