I'm looking for a simple and customizable tooltip plugin, either plain javascript or Jquery based, which has these features:
Bug free (Some that I've tried only show the tooltip sporadically and if you wave your mouse around they stop displaying)
Customizable (i.e being able to customize the css of the tooltip, select how long the tooltip stays in place after the mouse moves away, etc)
Must be able to programatically show/hide tooltips above any element, not just when the mouse is hovered.
I believe that qTip does what you are looking for. I've used it on several projects without problems. It's customizable and has a well documented api that allows you to show/hide it anywhere.