What about serious IDE support? I think that Cobra is behind on that part, which to me, is a very important point.
And by IDE I'm not talking about syntax color highlight only, but a real intellisense, project templates (win forms, WPF, MVC, etc.), refactor and so on.
The newest languages on the JVM are IDE enabled since day 1, such as: Ceylon (Eclipse), Kotlin (IntellijIDEA), Xtend (Eclipse), Scala (Eclipse), Gosu (IntellijIDEA), Fantom (Eclipse), Groovy (Eclipse), Golo (NetBeans) even Jython (Eclipse)
On the .NET side, most important/active ones are on Visual Studio (C#, VB.NET, F#, C++CLI, Phalanger, Oxygene, Nemerle, IronPython)
There is a VS addin for Cobra but last update was 8 months ago.
Developers that are familiar with those IDEs will quickly get into Cobra if it is well integrated on it, hence it will be easier to promote it