This was a trade-off I went with. One thing that I learned from years of hacking on haskell-mode is that adding an option for every little decision adds up to a

This was a trade-off I went with. One thing that I learned from years of hacking on haskell-mode is that adding an option for every little decision adds up to a brittle user-experience. If you want this, enable that. If you want to enable that, install this. And so on. A survey showed that most people used about 20% of the features available in haskell-mode. In the case of Intero I made every decision for the user; there are no customization options in the mode, and it leads to long (first-time) start-ups like this. But in the end I'd rather wait a minute and have every project always work reliably (and this isn't unheard-of for IDEs). It does build a version of intero for each project environment, because the GHC version and package set may differ. This is in contrast to e.g. ghc-mod or hdevtools which is locked to a specific GHC version, so switching between projects is not smooth.