You obviously have never used it to make such comments:
1.) It's not a gimmick. For the iPhone as it currently looks - it's not necessary. But if Apple starts to make a smaller version that either slides or flips with a touch sensitive screen i.e., LG chocolate, Venus, or Voyager than it makes total sense. When the phone is closed and locked there is no vibration letting you know that you can not accidently engage any keys. With the phone unlocked and haptic - you can answer it without flipping it open or sliding the bottom panel down. This would also be very helpful to play music with the phone still closed.
2.) Of course haptic does not tell you what you just did- who says it does? Only Robby the Robot tells you that.
3.) It is good for for turning the speakerphone key on/off very fast.