- Lots of new built-in primitives, such as functions for list
        manipulation and integer arithmetic. See the manual for a
        complete list. All primops are now available in the set
        `builtins`, allowing one to test for the availability of primop
        in a backwards-compatible way.
    
      - Real let-expressions: `let x = ...;
                                                        ... z = ...; in ...`.

  - New commands `nix-pack-closure` and `nix-unpack-closure` than can be
    used to easily transfer a store path with all its dependencies to
    another machine. Very convenient whenever you have some package on
    your machine and you want to copy it somewhere else.

  - XML support:
    
      - `nix-env -q --xml` prints the installed or available packages in
        an XML representation for easy processing by other tools.
    
      - `nix-instantiate --eval-only
                                                        --xml` prints an XML representation of the resulting term. (The
        new flag `--strict` forces ‘deep’ evaluation of the result,
        i.e., list elements and attributes are evaluated recursively.)
    
      - In Nix expressions, the primop `builtins.toXML` converts a term
        to an XML representation. This is primarily useful for passing
        structured information to builders.

  - You can now unambiguously specify which derivation to build or
    install in `nix-env`, `nix-instantiate` and `nix-build` using the
    `--attr` / `-A` flags, which takes an attribute name as argument.
    (Unlike symbolic package names such as `subversion-1.4.0`, attribute
    names in an attribute set are unique.) For instance, a quick way to
    perform a test build of a package in Nixpkgs is `nix-build
            pkgs/top-level/all-packages.nix -A
            foo`. `nix-env -q
            --attr` shows the attribute names corresponding to each derivation.

  - If the top-level Nix expression used by `nix-env`, `nix-instantiate`
    or `nix-build` evaluates to a function whose arguments all have
    default values, the function will be called automatically. Also, the
    new command-line switch `--arg
            name
            value` can be used to specify function arguments on the command
    line.

  - `nix-install-package --url
            URL` allows a package to be installed directly from the given URL.

  - Nix now works behind an HTTP proxy server; just set the standard
    environment variables `http_proxy`, `https_proxy`, `ftp_proxy` or
    `all_proxy` appropriately. Functions such as `fetchurl` in Nixpkgs
    also respect these variables.

  - `nix-build -o
            symlink` allows the symlink to the build result to be named
    something other than `result`.

  - Platform support:
    
      - Support for 64-bit platforms, provided a [suitably patched ATerm
        library](http://bugzilla.sen.cwi.nl:8080/show_bug.cgi?id=606) is
        used. Also, files larger than 2 GiB are now supported.
    
      - Added support for Cygwin (Windows, `i686-cygwin`), Mac OS X on
        Intel (`i686-darwin`) and Linux on PowerPC (`powerpc-linux`).
    
      - Users of SMP and multicore machines will appreciate that the