Orange, you quoted my question but didn't answer it. -10 points.
Thanks templar and pwn, those are both pretty good ideas. Pwn, as for your comments on what else the orbital does, those are both at the cost of a mule (You're sacrificing about 140 minerals of value with supply drop, assuming an SCV misses out on 6 mining trips making a depot) and scan is somewhat of a gambit (where do I think his tech/army is?), since if you mess up scanning the main of a zerg who hides his lair tech at his natural, or you only find gateways of the toss and no army, that scan is near worthless obviously.
In HoTS, maybe the MULE will no longer be a prototype and won't break down so quickly. I can't wait for the river of tears if that happens!