updated limitations section

docs/limitations.rst

@@ -12,7 +12,11 @@ certain limitations:
 - Multiple inheritance relationships on the C++ side cannot be mapped to
 - Multiple inheritance relationships on the C++ side cannot be mapped to
   Python.
   Python.
 
 
-Both of these features could be implemented but would lead to a significant
+- The NumPy interface ``pybind11::array`` greatly simplifies accessing
+  numerical data from C++ (and vice versa), but it's not a full-blown array
+  class like ``Eigen::Array`` or ``boost.multi_array``.
+
+All of these features could be implemented but would lead to a significant
 increase in complexity. I've decided to draw the line here to keep this project
 increase in complexity. I've decided to draw the line here to keep this project
 simple and compact. Users who absolutely require these features are encouraged
 simple and compact. Users who absolutely require these features are encouraged
 to fork pybind11.
 to fork pybind11.