The major improvements are:

 + Support for 64-bit platforms.
 + Native amd64 codegen.
 + New platforms: AMD64/Linux, AMD64/FreeBSD, HPPA/HPUX,
    PowerPC/AIX, X86/Darwin.
 + Support for specifying default Int.int, Word.word, and Real.real
    types at compile-time.

MLton has the following features.

 + Portability.
  Runs on the following platforms.
  o AMD64: Linux, FreeBSD.
  o HPPA: HPUX (11.00 and above), Linux (Debian).
  o PowerPC: AIX (5.1 and above), Darwin (Mac OS X), Linux (Debian,
Fedora).
  o Sparc: Linux (Debian), Solaris (8 and above).
  o X86: Cygwin/Windows, Darwin (Mac OS X), FreeBSD, Linux, MinGW/
Windows,
     NetBSD, OpenBSD.
 + Robustness.
  o Supports the full SML 97 language as given in The Definition of
     Standard ML.
  o A complete implementation of the Basis Library.
  o Generates standalone executables.
  o Compiles large programs (hundreds of thousands of lines).
  o Support for large amounts of memory (up to 4G on 32-bit systems,
     more on 64-bit systems).
  o Support for large arrays (up to 2G elements).
  o Support for large files (using 64-bit file positions).
 + Performance.
  o Executables with excellent running times.
  o Native integers, reals, and words (untagged and unboxed).
  o Unboxed native arrays.
  o Multiple garbage collection strategies.
  o Fast arbitrary-precision arithmetic based on the GnuMP.
 + Tools.
  o Source-level profiling of both time and allocation.
  o ML-Lex lexer generator.
  o ML-Yacc parser generator.
  o ML-NLFFIGEN.
 + Extensions.
  o Simple and fast C FFI for calling from SML to C and from C to SML.
  o The ML Basis system for programming in the very large.
  o Libraries for C pointers, continuations, interval timers, random
     numbers, resource limits, resource usage, signal handlers,
     system logging, threads, and heap save and restore.

For more information, go to the MLton home page.

  http://mlton.org/

Enjoy!