Yet another update to the top-level README.txt file

README.txt

@@ -48,24 +48,31 @@ ENVIRONMENTS
 
     - The Cygwin environment.  Instructions for installation of Cygwin on a
       Windows system are provided in the following paragraph, "Installing
-      Cygwin".  Cygwin is a very convenient environment, especially if you
-      need to integrate with Windows tools.  But the compile times are
-      very slow.
-
-    - The MSYS environment.  However, I have little experience that
-      configuration and it will not be discussed in this README file.
-      See http://www.mingw.org/wiki/MSYS if you are interested in
-      using MSYS.  People report to me that they have used MSYS
-      successfully.
+      Cygwin".  Cygwin is a mature, well-tested, and very convenient
+      environment.  It is especially expecially convenient if you  need to
+      integrate with Windows tools.  Downsides are that the installation
+      time is very long and the compile times are very slow.
 
     - Ubuntu/bash shell under Windows 10.  This is a new option under
       Windows 10.  See the section "Ubuntu Bash under Windows 10" below.
       This is an improvement over Cygwin if your concern is compile time;
-      its build performance is comparable to native Linux.
+      its build performance is comparable to native Linux.  It also installs
+      in a tiny fraction of the time as Cygwin, perhaps 20 minutes for
+      the basic Ubuntu install (vs. more than a day for the complete Cygwin
+      install).
+
+    - The MSYS environment.  I have no experience using the MSYS environment
+      and that configuration will not be discussed in this README file.
+      See http://www.mingw.org/wiki/MSYS if you are interested in
+      using MSYS.  People report to me that they have used MSYS
+      successfully.  I suppose that the advantages of the MSYS environemnt
+      is that it is closer to a native Windows environment and uses only a
+      minimal of add-on POSIX-ish tools.
 
     - NuttX can also be installed and built on a native Windows system, but
       with some potential tool-related issues (see the discussion "Native
-      Windows Build" under "Building NuttX" below).
+      Windows Build" under "Building NuttX" below).  GNUWin32 is used to
+      provide compatible native windows tools.
 
 Installing Cygwin
 -----------------
@@ -101,6 +108,9 @@ Installing Cygwin
      "Publishing".  You can try omitting KDE, Gnome, GTK, and other
      graphics packages if you don't plan to use them.
 
+     Perhaps a minimum set would be those packages listed below for the
+     "Ubuntu Bash under Windows 10" installation?
+
   After installing Cygwin, you will get lots of links for installed
   tools and shells.  I use the RXVT native shell.  It is fast and reliable
   and does not require you to run the Cygwin X server (which is neither