A small sample of reasons why the Scala standard library (especially collections) might need rewriting (most taken or modified from Paul Phillips talks on the Scala Collections library):
scala> 555555555.round // LOL
res0: Int = 555555584
scala> List("a", "b", "c").toSet() // seen this when learning Scala first time. ROFL.
res2: Boolean = false
scala> List(1, 2) ::: List("a", "b") // it'd be funny if you didn't care.
res3: List[Any] = List(1, 2, a, b)
scala> List(1, 2, 3) contains "wtf?" // LMAO if it didn't hurt so much
res5: Boolean = false
I might add more to the Gist in the link later. Thoughts? Comments?