The usefulness of this feature depends heavily on what you ask, and the response rate.

Customers don't want to rate their ticket experience, they want to get on with their life. It's very difficult to strike the right balance between gaining a genuine insight and causing an annoyance. Even a simple "was it good for you: yes/no" question can end up as the latter (and also not necessarily anything of the former).

It's something we're looking towards in future (on the endless todo list!), but for us we'd be looking to have a good deal of control about who and what we ask to the point we'd do this via some form of extension / integration rather than a core helpdesk feature. Thus we'd "just" (selectively?) include a follow-up survey link in an email footer for certain queues or requesters etc. (or combinations of both?) and/or send a separate follow-up email after a ticket was closed.

It's a huge request to add anything genuinely useful in this area. From my perspective we'd be looking at ensuring the necessary API options are available for smooth integration (i.e. without having to rewrite our integration code every x releases); because we didn't get to this on the todo list it's not something we evaluated properly to say what's missing (if anything)...

If you think a simple 5 star rating system is any use by itself (I guess the type of thing you were asking them to add in Cerberus?) then I suggest you take a look at any forum and see how many of the forum threads end up with a star rating (let alone anything approaching a meaningful one you can actually use for any business purpose). Those things exist on every major forum software now I think, but in my experience nobody uses the feature... waste of time.

This should be easily possible with the new Virtual Attendant functionality. There's an event for tickets closing, and a custom action could send out a survey when certain conditions are met.