Better "pitch" in the main documentation page. Added thanks to Tim Head,

which were overdue.

doc/index.rst

@@ -3,21 +3,20 @@ Welcome to the uncertainties package
 ====================================
 
 The `uncertainties package`_ is a free, cross-platform program that 
-handles calculations with **numbers with uncertainties** (like 
-3.14±0.01).  It also transparently yields the **derivatives** of any 
-expression (these derivatives are used for calculating uncertainties).
-
-Whatever the complexity of the calculation, this package returns the
-result with its uncertainty as predicted by linear `error propagation
-theory`_.  In particular, it handles **correlations** between
-variables, which sets it apart from many existing error propagation
-codes.
-
-Calculations involving numbers with uncertainties are made **very 
-simple** thanks to this package.  In fact, it :ref:`transparently 
-<derivatives>` calculates the `numerous derivatives`_ required by linear 
-error propagation theory.  Performing the same calculations by hand and 
-implementing the resulting formulas is generally quite tedious.
+transparently handles calculations with **numbers with uncertainties** 
+(like 3.14±0.01).  It can also yield the **derivatives** of any 
+expression.
+
+The :mod:`uncertainties` package **takes the pain and complexity out** 
+of dealing with uncertainty calculations. Error propagation is not to be 
+feared anymore!
+
+Whatever the complexity of the calculation, this package returns the 
+result with its uncertainty as predicted by linear `error propagation 
+theory`_. It automatically :ref:`calculates derivatives <derivatives>` 
+and uses them for calculating uncertainties. **Correlations** between 
+variables are thus autoamatically handled, which sets it apart from many 
+existing error propagation codes.
 
 Calculations of results with uncertainties, or of derivatives, can
 either be performed in an **interactive session**, or in **programs**
@@ -31,11 +30,12 @@ Let's now see how to use these unique features!
 An easy-to-use calculator
 =========================
 
-Calculations involving **numbers with uncertainties** can be performed
-even without knowing anything about the Python_ programming language.
-After `installing this package`_ and `invoking the Python
-interpreter`_, calculations with automatic error propagation can be
-performed directly and transparently:
+Calculations involving **numbers with uncertainties** can be performed 
+even without knowing anything about the Python_ programming language. 
+After `installing this package`_ and `invoking the Python interpreter`_, 
+calculations with **automatic error propagation** can be performed 
+**transparently** (i.e., through the usual syntax for mathematical 
+formulas):
 
   >>> from uncertainties import ufloat
   >>> from uncertainties.umath import *  # sin(), etc.
@@ -45,8 +45,9 @@ performed directly and transparently:
   >>> sin(2*x)  # In a Python shell, "print" is optional
   0.90929742682568171+/-0.083229367309428481
 
-Thus, existing calculation code designed for floats can be run with
-numbers with uncertainties with :ref:`no or little modification <user guide>`.
+Thus, existing calculation code designed for regular numbers can run 
+with numbers with uncertainties with :ref:`no or little modification 
+<user guide>`.
 
 .. index:: correlations; simple example
 
@@ -256,20 +257,19 @@ Acknowledgments
 ===============
 
 The author wishes to thank Arnaud Delobelle, Pierre Cladé, and Sebastian 
-Walter for very useful technical input.  Patches by Pierre Cladé and 
-José Sabater Montes are gratefully acknowledged. I would also like to 
-thank Joaquin Abian, Jason Moore, Martin Lutz and many other users for 
-their feedback and suggestions, which greatly helped improve this 
-program. I am also grateful to the Linux distribution maintainers of 
-this package, and to Christoph Gohlke for including it in his Base 
+Walter for very useful technical input.  Patches by Pierre Cladé, Tim 
+Head, and José Sabater Montes are gratefully acknowledged. I would also 
+like to thank Joaquin Abian, Jason Moore, Martin Lutz and many other 
+users for their feedback and suggestions, which greatly helped improve 
+this program. I am also grateful to the Linux distribution maintainers 
+of this package, and to Christoph Gohlke for including it in his Base 
 distribution of scientific Python packages for Windows.
 
 .. _Python: http://python.org/
 .. _error propagation theory: http://en.wikipedia.org/wiki/Propagation_of_uncertainty
 .. _invoking the Python interpreter: http://docs.python.org/tutorial/interpreter.html
 .. _setuptools: http://pypi.python.org/pypi/setuptools
 .. _download: http://pypi.python.org/pypi/uncertainties/#downloads
-.. _numerous derivatives: http://en.wikipedia.org/wiki/Propagation_of_uncertainty#Non-linear_combinations
 .. _donating $5: https://www.paypal.com/cgi-bin/webscr?cmd=_s-xclick&hosted_button_id=4TK7KNDTEDT4S
 .. _Eric O. LEBIGOT (EOL): mailto:eric.lebigot@normalesup.org
 .. _BSD license: http://creativecommons.org/licenses/BSD/