hoist_vars is pretty bad, it seems. cancelled it for now.

bin/uglifyjs2

@@ -41,11 +41,8 @@ if (ARGS.h || ARGS.help) {
 
 var files = ARGS._.slice();
 
-if (files.length == 0) {
-    sys.error("ERROR: No input files.");
-    sys.puts(optimist.help());
-    process.exit(1);
-}
+if (files.length == 0)
+    files = [ "-" ];
 
 if (files.indexOf("-") >= 0 && ARGS.source_map) {
     sys.error("ERROR: Source map doesn't work with input from STDIN");

lib/compress.js

@@ -65,7 +65,7 @@ function Compressor(options, false_by_default) {
         booleans      : !false_by_default,
         loops         : !false_by_default,
         hoist_funs    : !false_by_default,
-        hoist_vars    : !false_by_default,
+        //hoist_vars    : !false_by_default, // XXX: turns out, this is really bad
 
         warnings      : true
     });