Giles Alexander wrote a blog post recently about the downsides of Scala. I figured I'd give an alternate viewpoint, considering a) newsrdr was written in Scala and b) this is my first time using Scala. Note that this is nowhere near comprehensive, since I'm still learning and all.

Compilation Times

For a test, I ran a completely clean rebuild of newsrdr from the github repo from my late-2013 13" MacBook Pro:

harry:newsrdr mooneer$ time ./sbt package
Detected sbt version 0.12.3
Using /Users/mooneer/.sbt/0.12.3 as sbt dir, -sbt-dir to override.
[info] Loading project definition from /Users/mooneer/newsrdr/project/project
[info] Loading project definition from /Users/mooneer/newsrdr/project
[info] Set current project to newsrdr (in build file:/Users/mooneer/newsrdr/)
[info] Updating {file:/Users/mooneer/newsrdr/}newsrdr...
[info] Resolving org.slf4j#slf4j-api;1.6.1 ...
[info] Done updating.
[info] Compiling 5 CoffeeScripts to /Users/mooneer/newsrdr/target/scala-2.10/resource_managed/main/webapp/js
[info] Generating /Users/mooneer/newsrdr/target/scala-2.10/resource_managed/main/rebel.xml.
[info] Compiling Templates in Template Directory: /Users/mooneer/newsrdr/src/main/webapp/WEB-INF/templates
SLF4J: Failed to load class "org.slf4j.impl.StaticLoggerBinder".
SLF4J: Defaulting to no-operation (NOP) logger implementation
SLF4J: See http://www.slf4j.org/codes.html#StaticLoggerBinder for further details.
[info] Compiling 34 Scala sources to /Users/mooneer/newsrdr/target/scala-2.10/classes...
[warn] there were 4 deprecation warning(s); re-run with -deprecation for details
[warn] one warning found
[info] Packaging /Users/mooneer/newsrdr/target/scala-2.10/newsrdr_2.10-0.1.0-SNAPSHOT.war ...
[info] Done packaging.
[success] Total time: 61 s, completed Dec 1, 2013 6:48:29 PM

real 1m10.330s
user 2m36.123s
sys 0m3.797s
harry:newsrdr mooneer$

The part that felt like it took the longest appeared to be the CoffeeScript compilation, not the compilation of the Scala code. Compile times will probably be far less in normal development, though YMMV. Recent versions of sbt can now take advantage of parallelism to improve compile times, making the hit far less than in the past.

Integration with the JVM

This was a big winner for me. For instance, there is already a very good task scheduling library called Quartz written in Java, which includes built-in clustering support. Having to duplicate this effort in Scala would honestly not have been a good use of my time. Some other things (such as fetching using HTTP) were also far easier using Oracle's libraries. It also works the other way--if I ever needed to, I could release a JAR that Java developers can use in their own applications.

Syntax/semantics: not all that bad

There is definitely a Scala way of doing things, much like how there is a Java way of doing things, a C# way of doing things, etc. The advantages and disadvantages of operator overloading are definitely in play in Scala, and basically boils down to the library developer. If someone overloads an operator in an unexpected way, I'm more apt to blame the library developer rather than the language itself. Basically, Scala gives back some of the power that's lost when using Java, and that's a good thing.

Even if we admit that operator overloading is a negative for the language, the language itself still grants far easier entry into functional programming than some of the others out there. For instance, in the past I tried Haskell and kept banging my head against the wall. Some day I'll probably try it again, but for now Scala allows me to get stuff done.

Types are way more flexible

I've found the Scala type system to be extremely flexible. For example, traits effectively act as mixins for classes; the equivalent in Java would be extremely difficult to implement. The other advantage of having types everywhere is that you can do a lot more checking at a static level vs. finding out the hard way that a Content-Length header isn't supposed to be a string. This helps significantly with program correctness.

Conclusion

For me, Scala was perfectly accessible. One does need to define "accessible", though: I have significant programming experience from my day job as well as previous personal projects. I imagine someone who have never developed before would be better off starting with something like Java or Python first. For anyone interested, there was a Scala course on Coursera recently that's highly recommended. Even though the course is done for now, the materials are still up and can be worked through. There's also a tutorial written especially for Java developers (warning: PDF).

Would I write newsrdr in Scala again? Yes. Future projects? Depends on the project.