My girl (4) is wonderful, brilliant and slow as all get out. Walking, eating, everything. Drives me up the wall! But what I've learned, darn-it-all, is that it is my problem, not hers. I give her advance warning when we have to move it, like if there has to be a quick transition, but other than that, I've had to learn to give her extra time for EVERYTHING. Pre-school has helped (somewhat) with that. One thing I've done is had her wait for me when she REALLY, REALLY wants to do something. I ask her how she feels. "Mama, I just want to GO." Yeah, that's how someone feels when they have to wait for someone else.
And like L., thought of the cattle prod: ) Oh, the imagination takes us places when we are frustrated.
Seriously though, some aspects of her slow nature I wouldn't change for anything. She's also slow to anger, she doesn't get frustrated very easily, she's methodical. She's just on a different speed than me.