Changes made since 2.10:

\begin{itemize}

\item Multi-parameter type classes are fully implemented.  There is more
  sharing of dictionaries than in 2.10, so there's a chance that
  efficiency will increase a little too.

\item Error messages from the type checker should be noticeably improved

\item Warnings for unused bindings @-fwarn-unused-names@.

\item The "boing" example works, and many other minor bug fixes.

\item Can only be built with 2.10 or later; committed to Haskell 1.4
  module system and libraries.  Much cruft removed as a result.

\item Dramatic clean-up of the @PprStyle@ stuff.  No explicit "sty"
parameters now; it's all handled under the hood in @Outputable.lhs@.

\item The type @Type@ has been substantially changed.  Usage types have
  gone away entirely.  Type is parameterised wrt the "flexi" slot
  in type variables, rather than wrt the type variable itself.
  That means that many instance decls become much simpler, because
  they are polymorphic in the "flexi" slot rather than needing
  (say) @Outputable@ on the type variable.

\item The dictionary for each class is represented by a new
  data type for that purpose, rather than by a tuple.  That in
  turn means that @Type@ can be a straightforward instance of @Eq@ and
  @Ord@ No need for @eqSimpleTy@, @eqTy@.

\item The resulting compiler is just slightly (2%) shorter than the
  old one in terms of source code size.

\item Fix bug in posix signal handling.

\item @Int@ and @Word@ rewritten to use unboxed types and operations.

\item Removed @ghc/Error.{lhs,hi-boot}@

\item Moved contents of @Error@ to @GHCerr@ + adjusted
  import lists of files that use old Error functionality.

\item Moved @seqError@ from @Prelude@ to @GHCerr@.

\item Fix a misleading type checker error msg.

\item Fix a bug in @floatBind@ in @Simplify.lhs@

\item Better failure message when entering an unimplemented instance method

\item The Installation Guide is now in SGML format.  SGML-Tools 1.0.3
or later are required (check @http://www.xs4all.nl/~cg/sgmltools/@).
The index generation isn't automatic yet, but will hopefully be fixed
for the next release.

\end{itemize}