Personally, I'm most glad to see that Applicative is finally a superclass of Monad.

Whoa, I never thought that would get fixed. It's been, what, 20 years? :-)

So why wasn't it done earlier? Is there going to be any code breakage with that?

I think Applicative was introduced within the last 10 years. The paper that introduced them was published in 2008 (Applicative Programming with Effects, Conor McBride and Ross Paterson)

That just drives home how long it's been the case that Applicative wasn't a superclass of Monad! ;)

There have been deprecation warnings (since 7.8?) about the AMP:

https://wiki.haskell.org/Functor-Applicative-Monad_Proposal#...

There's a list of breakage at:

https://www.fpcomplete.com/blog/2015/03/stackage-ghc-7-10

(I'm not sure what portion of that is due to AMP.)

The type hole feature is pretty cool!

I learned how to solve some of my type-related puzzlement by redefining stuff as "undefined" and using HDevTools to see what type gets inferred.

Also I can't wait to see what wild stuff people will come up with using the typechecker plugin API

You've always been able to have type holes at the ghci prompt - wrap your expression in a lambda and see what's inferred as the first argument.

That's not to say the ability to do it in the middle of a program isn't huge - it is! - but just a technique I have occasionally found quite useful that's available to those stuck on older versions of ghc.

Things still on the wishlist:

1. giving cabal the ability to sensibly manage packages (dependency resolution / uninstallation, etc.)

2. Arbitrary-precision floating point arithmetic through openfp (corollary to the use of gmp to accomplish the separation between Int and Integer).

3. Arbitrary-radix integer literals (e.g. as in Erlang).

Regardless, huge steps forward with this update :)

In the release notes linked in the announcement, the link to the migration guide points to the release notes themselves. The right link should be: https://ghc.haskell.org/trac/ghc/wiki/Migration/7.10

Sometimes the most relevant discussion takes place on reddit's /r/haskell.

http://www.reddit.com/r/haskell/comments/30gyie/announce_ghc...

Michael Snoyberg sez 1-4 months before a GHC7.10 Stackage release. Awesome! I love Stackage

Yeah, Stackage is God-sent.