The FPComplete guys will probably have it up on Stackage in a few days. You can still use it by adding the tarball to your stack.yml, and maybe adding the 'allow-newer: true' flag:

https://www.reddit.com/r/haskell/comments/4kdb74/is_a_stacka...

I'm looking forward to trying out the new debugging support: gdb was unusable with older GHCs.

Implicit callstacks are cool: Remember that you can hide the parameter inside of your application's main monad:

    type MyApplicationM a = (?l :: CallStack) => StateT ConnectionPool IO a

I've certainly run into a lot of the other stuff too. Good release all-around!