This is a big deal. This is one of the reasons I'm so productive in Scala (Higher kinded types). When evaluating F# vs. Scala for our latest project it was the single big thing that drove our team to pick Scala, so the fact that Ceylon is adding it could really help pick up users from the functional side.

I also think it says a lot about the language designer Gavin King. He seems to take feedback from the community and legitimately weigh the pros and cons. If I remember originally he wasn't sure HKTs were useful, but it seems he's come around after hearing various arguments for them.