Update README to describe QtPy usefulness when migrating between Qt b…

…indings/versions (#301)

* Update README.md to add a line for QtPy usefulness when migration between Qt bindings/versions
* Apply suggestions from code review to README.md

Co-authored-by: CAM Gerlach <[email protected]>
Co-authored-by: Carlos Cordoba <[email protected]>

README.md

@@ -21,9 +21,10 @@ write applications using a single API call to either PyQt or PySide.
 It provides support for PyQt5, PyQt6, PySide6, PySide2 using the Qt5 layout
 (where the QtGui module has been split into QtGui and QtWidgets).
 
-Basically, you can write your code as if you were using PySide2
-but import Qt modules from `qtpy` instead of `PySide2` (or `PyQt5`)
+Basically, you can write your code as if you were using PyQt or PySide directly,
+but import Qt modules from `qtpy` instead of `PyQt5`, `PyQt6`, `PySide2`, or `PySide6`.
 
+Accordingly, when porting code between different Qt bindings (PyQt vs PySide) or Qt versions (Qt5 vs Qt6), QtPy makes this much more painless, and allows you to easily and incrementally transition between them. QtPy handles incompatibilities and differences between bindings or Qt versions for you while keeping your project running, so you can focus more on your own code and less on keeping track of supporting every Qt version and binding. Furthermore, when you do want to upgrade or support new bindings, it allows you to update your project module by module rather than all at once.  You can check out examples of this approach in projects using QtPy, like [git-cola](https://github.com/git-cola/git-cola/issues/232).
 
 ### Attribution and acknowledgments