Haptic feedback is a very useful way of letting the user know they have successfully performed an action. For example, it's a simple way to let the user know they clicked a button instead of having to wait for something to happen to know it was clicked.
But haptic feed is not something you'd want to use wherever you can.
While there are users who don't mind haptic feedback, there are users who hate it with a passion.
But I'm one of those users who have haptic feedback on because I find it quite useful especially when using the keyboard, and my S6 has a physical back button which I would like to know if it was clicked or not. But if it were to happen every time I click a button on the screen it won't be a very pleasant experience.
This article "Why I hate haptic feedback" has a few sensible points. But what I would like to highlight the most is,
But after you’ve been dealing with every type of smartphone for four years, you begin to notice the subtleties in software, visual indicators that a tap was accepted – a tiny flash around an icon, for example.
If you want to incorporate haptic feedback in your mobile app or website, first consider if there is a better visual alternative you can use.
The set of interactions you mentioned, off the top of my head you can do the following,
- Add an item to the cart : Pulse effect on the shopping cart icon. And increase cart items count.
- Add an item to the wish list: Pulse effect on the wish list icon.
- Delete an item: Animation - Fade out / slide out and disappear.
- Checkout steps: I'm guessing you mean a button click? In which case a highlight around the button or changing the color, adding an subtle but noticeable effect on the button is enough.
- End of checkout: You really don't need haptic feedback for this.