nixpkgs manual introduction: improve

- make line wrapping more consistent (overlong lines)
- don't stress the manual is *only* for contributors,
  as it does contain some user-guide parts, including the intro itself
- since March our Hydra publishes binaries immediately,
  not waiting for channel update

1 files changed, 22 insertions, 17 deletions

diff --git a/doc/introduction.md b/doc/introduction.md
index 618251a6e15..96a5571b426 100644
--- a/doc/introduction.md
+++ b/doc/introduction.md
@@ -6,13 +6,14 @@ date: 2015-11-25
 
 # Introduction
 
-The Nix Packages collection (Nixpkgs) is a set of over 30,000 packages for the
-[Nix package manager](http://nixos.org/nix/), released under a [permissive MIT/X11 license](https://github.com/NixOS/nixpkgs/blob/master/COPYING).
-Packages are available for several architectures, and can be used with the Nix package manager
-on most GNU/Linux distributions as well as NixOS.
-
-This manual describes how to write packages for the Nix Packages collection
-(Nixpkgs). Thus it’s for packagers and developers who want to add packages to
+The Nix Packages collection (Nixpkgs) is a set of thousands of packages for the
+[Nix package manager](http://nixos.org/nix/), released under a
+[permissive MIT/X11 license](https://github.com/NixOS/nixpkgs/blob/master/COPYING).
+Packages are available for several platforms, and can be used with the Nix
+package manager on most GNU/Linux distributions as well as NixOS.
+
+This manual primarily describes how to write packages for the Nix Packages collection
+(Nixpkgs). Thus it’s mainly for packagers and developers who want to add packages to
 Nixpkgs. If you like to learn more about the Nix package manager and the Nix
 expression language, then you are kindly referred to the [Nix manual](http://nixos.org/nix/manual/).
 
@@ -20,29 +21,33 @@ expression language, then you are kindly referred to the [Nix manual](http://nix
 
 Nix expressions describe how to build packages from source and are collected in
 the [nixpkgs repository](https://github.com/NixOS/nixpkgs). Also included in the
-collection are Nix expressions for [NixOS modules](http://nixos.org/nixos/manual/index.html#sec-writing-modules). With
-these expressions the Nix package manager can build binary packages.
+collection are Nix expressions for
+[NixOS modules](http://nixos.org/nixos/manual/index.html#sec-writing-modules).
+With these expressions the Nix package manager can build binary packages.
 
 Packages, including the Nix packages collection, are distributed through
 [channels](http://nixos.org/nix/manual/#sec-channels). The collection is
 distributed for users of Nix on non-NixOS distributions through the channel
 `nixpkgs`. Users of NixOS generally use one of the `nixos-*` channels, e.g.
-`nixos-15.09`, which includes all packages and modules for the stable NixOS
-15.09. The channels of the stable NixOS releases are generally only given
+`nixos-16.03`, which includes all packages and modules for the stable NixOS
+16.03. The purpose of stable NixOS releases are generally only given
 security updates. More up to date packages and modules are available via the
 `nixos-unstable` channel.
 
 Both `nixos-unstable` and `nixpkgs` follow the `master` branch of the Nixpkgs
-repository, although both do lag the `master` branch by generally [a couple of days](http://howoldis.herokuapp.com/). Updates to a channel are distributed as
-soon as all tests for that channel pass, e.g. [this table](http://hydra.nixos.org/job/nixpkgs/trunk/unstable#tabs-constituents)
+repository, although both do lag the `master` branch by generally
+[a couple of days](http://howoldis.herokuapp.com/). Updates to a channel are
+distributed as soon as all tests for that channel pass, e.g.
+[this table](http://hydra.nixos.org/job/nixpkgs/trunk/unstable#tabs-constituents)
 shows the status of tests for the `nixpkgs` channel.
 
 The tests are conducted by a cluster called [Hydra](http://nixos.org/hydra/),
-which also builds binary packages from the Nix expressions in Nixpkgs. As soon
-as a channel is updated, the binaries are made available via a [binary cache](https://cache.nixos.org). Until the channel updates, binaries that have
-already been built, are available via [Hydra's binary cache](https://hydra.nixos.org).
+which also builds binary packages from the Nix expressions in Nixpkgs for
+`x86_64-linux`, `i686-linux` and `x86_64-darwin`.
+The binaries are made available via a [binary cache](https://cache.nixos.org).
 
 The current Nix expressions of the channels are available in the
 [`nixpkgs-channels`](https://github.com/NixOS/nixpkgs-channels) repository,
 which has branches corresponding to the available channels. There is also the
-Nixpkgs Monitor which keeps track of updates and security vulnerabilities.
+[Nixpkgs Monitor](http://monitor.nixos.org) which keeps track of updates
+and security vulnerabilities.