This is something that came to me when I was using Movable Type. Hitting Publish on a page required me to wait for it to finish all of its operations synchronously before I could continue to do anything. What I really wanted was to be able to save the page, trigger those events in the background, and only need to be notified in some way if things went wrong. With MeTal, we have that, but it still has limitations I want to overcome.
Right now, the UI for publishing is async -- when you send a page off to be published, you get a notification in the interface that X jobs have been queued, and you see them tick down in batches of fifty.
The bad news is that this still requires you to keep that particular page open to get any feedback about what's going on, which somewhat defeats the purpose.
I'm looking into several user-selectable possibilities for how feedback is provided.
Obviously this last one is only useful for hosts that allow scheduled tasks, but I have yet to find one running today that didn't.
Some other ideas that are orthogonal but also useful:
The main problem, then, isn't so much running the script as getting feedback about it back to the user in a timely way -- to honor the asynchronicity of the process all the way.