I've inherited a large scale codebase and it's been interesting to put it mildly. I agree with GP that Scala's power lends itself to building unnecessarily complex systems.

- Scala has a lot of cool, but sometimes confusing features. Implicits, companion classes, apply/unapply.

- our compile times are 5-10 minutes in CI. I'm sure we can make it go faster, but it requires digging into a 500 line SBT file.

- Scala seems to encourage building tangled webs of actors with Akka. I understand the benefits of actors. I think the benefits are overstated vs threads when you need less than 10k threads or so.