"When we say optional, we really do mean optional. The Committee will in NO way hold it against you if you choose not to answer any of these questions. (Maximum 250 words.)"
I wasn't planning on it. If I do, I'll probably do a funny video.
I plan to write them all. Like @"Cant Get Right" said above, they are "optional" but I think any serious candidate should write them. That's the general advice from admissions professionals, too.
Just FYI I had a friend who had a 2.9 uGPA, studied hard, got a 177 on the LSAT, then got admitted to nearly every T-14 school (including Harvard!). He ended up going to UVA on a full ride.
Send it in as soon as possible so that your name is higher on the list. That doesn't mean you should send it in right now, though. If your optional statement will make your application stronger, make sure to include it.