Gave credits to Peter S. Hollander for finding out the correct format of

the USB feature reports.
Improved the example.

examples/ViveTracker/ViveTracker.ino

@@ -32,5 +32,5 @@ void loop() {
 		uint16_t batteryLevel = 0;
 		tracker.setTrackerStatus(buttons, padX, padY, trigger, batteryLevel);
 	}
-	delay(300);
+	delay(10); // According to HTC's documentation the interval to send data should be at least 10 ms.
 }

src/ViveTrackerController.h

@@ -20,6 +20,13 @@
 #define VIVETRACKER_BUTTON_PADTOUCHED    (1 << 5)
 
 
+/*
+ * The format of the USB HID feature reports is unfortunately not correct in HTC's documentation.
+ * Fortunately Peter S. Hollander was able to find out the correct format of the feature reports,
+ * and he was kind enough to share the details on his blog: 
+ * http://www.talariavr.com/blog/vive-tracker-initial-documentation/
+ */
+
 /**
  * \struct Vive Tracker Feature Report 0xB3
  */