"By most measures, Scala is not a simple language to learn. While there are lots of languages that are large in scope and features, most can be learned over time. Scala fall short by requiring you to learn at least 75% before you can do anything meaningful. When I first started out with some basic scripting this didn’t appear to be the case, however; once I tackled a real project, I realized how limited my knowledge really was. For those that think you’ll coast by because you’re a Java expert, think again. My Java knowledge is extensive and the parallels between the language are few and far between."
part of me wonders if this is inevitable, and a good thing. many problems don't require expert tools and expert teams. joe blo can write a blog on appengine, and you can throw a bunch of college hire "consultants" on many business apps and be successful. Competence is relative. As problems get more complex (see Why Is Payroll Hard) you need more expert teams and more expert tools, your average enterprise java team of people who work 9-5, have a nice family and a powerboat hobby (but perfectly competent, by most standards!), can no longer successfully manage the complexity. Maybe they can't grasp scala, maybe they just aren't interested in grasping scala. But there is a set of problems which you need experts to solve, and experts want sharper tools. like git, a macbook, and not-java.
 which is, you know, how people get turned on to FP in the first place. "you don't find it, it finds you"
Really. Drastically accelerates development. Sounds suspiciously like he found himself a Silver Bullet. And of course all of the little hiccups along the way that come with moving to a new(ish), less mature platform don't slow down development at all.
"While the Scala compiler invoked through a builder like Maven, or the command line provides workarounds for this, IDE’s such as Eclipse and NetBeans don’t fare as well. Although the Eclipse Scala plugin is supposed to support Joint Compilation out of the box, this has not been my experience thus far. As long as your not married to Eclipse, I’ve heard IntelliJ and Buildr are the best IDE’s for Scala development so you may want to opt for one those if going the Scala route."
Good thing actually compiling is not a frequent and crucial behavior in the development process otherwise these little quirks might really slow things down.
"In my case, I use Java for Servlets and REST via Jersey with the service and data access layers provided by Scala. This way Scala never has to call Java."
LOL. You know, because Hibernate or JdbcTemplate are just too gnarly to deal with. We need the brevity of Scala here! And a functional model for our service layer! Really, maybe if the guy was doing some highly concurrent app and was making the argument that Scala's Actor model greatly simplified things, that might be a plausible justification. But for some service and dao classes? Seriously? How do people justify these decisions with a straight face?
And yes, Hibernate really is that gnarly. Imlementing a rest/Jason interface in Clojure is vastly easier, never mind simpler.
Or Xtend, or Kotlin or Ceylon (though the second two haven't yet been widely released).