[gareth_at_work]

Scala had some of the same design goals as Ruby, especially the goal of being a pleasant language to live in on a daily basis. Mirah essentially removes the (theoretically, at least) performance advantage that Scala had over JRuby. Of course there is the issue of not being able to use MRI Ruby code with Mirah; overcoming that in a clean way would bring a lot of MRI folks over to Mirah.