diff --git a/README.md b/README.md
index 7d18e17..1faacd0 100644
--- a/README.md
+++ b/README.md
@@ -17,14 +17,55 @@ aster.src('src/**/*.js')
 .map(plugin1(optionsForPlugin1))
 .map(plugin2(optionsForPlugin2))
 // ...
-.subscribe(aster.runner);
+.subscribe(aster.runner({
+    onNext: (item) => {
+        console.log('>> %s'.yellow, item)
+    }
+}));
 ```
 
+When you create an `Observable`, you always pass 3 functions in this order: 
+- `successHandler`
+- `errorHandler`
+- `onCompleteHandler`
+
+The `success` or `error` handler is called for each processed event/item of the Observable stream, the `onComplete` handler when the stream is done (such as no more files to be processed).
+
+The default event handlers are:
+
+```js
+function onFile(file) {
+  console.log('>> %s'.yellow, file.path)
+}
+
+function onError(error) {
+  console.error(error.stack.red)
+}
+
+function onCompleted() {
+  console.log('Done.'.green)
+}
+```
+
+Where `onFile` is used for `onSuccess` and expects a `file` object with a `path`.
+
 ## API
 
 ### runner
 Type: [`Rx.Observer`](https://github.com/Reactive-Extensions/RxJS/blob/master/doc/api/core/observer.md)
 
+#### options.onSuccess
+
+Success event handler for individual item/event processed.
+
+#### options.onError
+
+Error event handler for individual item/event processed.
+
+#### options.onCompleted
+
+Completed handler for when entire stream of events/items of Observable has been processed.
+
 ## License
 
 [MIT License](http://en.wikipedia.org/wiki/MIT_License)
diff --git a/index.js b/index.js
index 78cad85..8d4ebe8 100644
--- a/index.js
+++ b/index.js
@@ -3,12 +3,34 @@
 var Rx = require('rx');
 require('colors');
 
-module.exports = Rx.Observer.create(function onFiles(files) {
-	console.log('Processing files...');
-
-	files.subscribe(Rx.Observer.create(
-		function onFile(file) { console.log('>> %s'.yellow, file.path) },
-		function onError(error) { console.error(error.stack.red) },
-		function onCompleted() { console.log('Done.'.green) }
-	));
-});
+
+var defaults = {
+  onNext: function(file) {
+    console.log('>> %s'.yellow, file.path)
+  },
+  onError: function (error) {
+    console.error(error.stack.red)
+  },
+  onCompleted: function () {
+    console.log('Done.'.green)
+  }
+}
+
+function defaultSubscriber(options) {
+  return function onFiles(files) {
+    console.log('Processing files...');
+
+    files.subscribe(Rx.Observer.create(
+      options.onNext || defaults.onNext,
+      options.onError || defaults.onError,
+      options.onCompleted || defaults.onCompleted
+    ));
+  }
+}
+
+module.exports = function(options) {
+  var subscriber = options.subscriber || defaultSubscriber
+  subscriber = typeof subscriber === 'function' ? subscriber(options) : subscriber
+
+  Rx.Observer.create(subscriber);
+}
diff --git a/package.json b/package.json
index 0064129..8bb106c 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "aster-runner",
-  "version": "0.1.1",
+  "version": "0.2.0",
   "description": "Task runner for aster.",
   "author": "Ingvar Stepanyan <me@rreverser.com> (https://github.com/RReverser)",
   "repository": "asterjs/aster-runner",
@@ -12,7 +12,7 @@
   ],
   "main": "index.js",
   "dependencies": {
-    "colors": "^0.6.2",
-    "rx": "^2.3.11"
+    "colors": "^1.1.2",
+    "rx": "^4.1.0"
   }
 }