diff --git a/README.md b/README.md
index b9cfb9e..14226a7 100644
--- a/README.md
+++ b/README.md
@@ -12,6 +12,11 @@ http://akkartik.name/lines.html
 * Undo/redo can be sluggish in large files. If things get sluggish, killing
   the process can lose data.
 
+* Large files may grow sluggish in other ways. I've noticed in 100KB files
+  that closing the window can take a few seconds. And it seems to take longer
+  in proportion to how far down my edits are. The phenomenon persists even if
+  I take out undo history.
+
 * The text cursor will always stay on the screen. This can have some strange
   implications: