Whether your experience at the company you're leaving has been pleasant or abysmal, an exit interview is still a good idea.
Even if they're not offering it, you should think about requesting one. Exit interviews allow you to officially thank your employer for the time you've spent there, the experience you've gained, and all you've learned in the process. It's also a great time to make sure you can rely on the higher-ups for a reference or even a future collaboration that is mutually beneficial. It also gives you an opportunity to provide some constructive criticism about the company, and politely explain what circumstances led to your leaving.
A good manager will value that information and use it to keep other high-value employees from jumping ship.