An essay that starts well, that has a strong opening, that's clear and concise and maybe has...maybe it starts with an anecdote that's powerful and sets things up and pulls the reader in, makes you want to know more and one in which the student seems, at least at that early going, to be in control and to know where this is going and is going to be a sure hand at guiding you through their argument...and that's really an impressive thing. It goes a long way towards smoothing over any bumps along the way; whereas, it's harder to recover. I've read many a fine essay that still has some fairly catastrophic opening sentence. It's really amazing. People have a block about it, I guess. Attend to that opening, people. Is basically what I say.