In a production environment, in which users do the same procedure many times per hour, any kind of delay, animation, "because we can" eye candy is a nuisance. Believe me. People click on things to get work done, not to be impressed by fancy stuff.
All my popovers appear instantly and I have to do extra effort for that (naming objects in the popover and go to object) because when users click on something they expect it to f'ing show, not to slowly fade from nowhereness into view in 500 milliseconds.
Some like it rough
thanks siplus...... performance vs eye candy. Sticking with performance for sure.