1. Delight is overblown, in my opinion. I think most of the people truly delighted by fancy animation are just other designers.
2. It's more useful to think about state when deciding when to animate. Could the user have trouble perceiving the change in state that just occurred? If so, then use an animation to help them visualize what happened. I believe this is the primary reason to use an animation - all others are vanity.
I think this is the only justified use of animation in UI, however I wasn't satisfied with the dilemma of increasing perceived transition while increasing perceived UI latency.
I found it's possible to get the best of both for event triggered state changes i.e clicking on stuff, by sticking to ease-out based transitions, where the start of the transition is instant and the end decelerates.
This makes it feel just as snappy as no animation, while still helping to communicate a transition, because we are more sensitive to the latency of the start of the transition when it's an event - since we are anticipating a reaction, which is satisfied as soon as it starts to react.