As others are going to say, I wish they spent some of the time optimizing the compile times, yes you can fix it with multi-projects and the incremental compiler but sometimes that doesn't work to well especially when you start to throw in advance scala features like macros. But maybe they are hoping the new backend helps, from the docs it looks like it may in some cases.
First off, macros are not just an advanced feature. They are experimental. Investments in tooling will always focus on official features first (not to say we ignore macros, but we have to prioritize).
We spend a lot of time optimizing the compiler. Several big users have reported nice speed ups on 2.11. I won't quote numbers (too hard to benchmark accurately), but encourage you to give it a go. The upgrade is easy.
Also, it's just generally a good idea to design your software so that it can be compiled incrementally in smaller modules.
