Describe the nature of Python 3 roughness

docs/python3.rst

@@ -35,8 +35,10 @@ Recommendations
 
 Unless you require absolute compatibility, you should be fine with Python 3
 nowadays. Most libraries and Flask extensions have been ported by now and
-using Flask with Python 3 is generally a smooth ride. However, you might
-occasionally encounter encoding problems.
+using Flask with Python 3 is generally a smooth ride. However, keep in mind
+that most libraries (including Werkzeug and Flask) might not quite as stable
+on Python 3 yet. You might therefore sometimes run into bugs that are
+usually encoding-related.
 
 The majority of the upgrade pain is in the lower-level libararies like
 Flask and Werkzeug and not in the actual high-level application code.  For