I'd like to hear more about exercising options early. I had no idea that could be done. Not that I'll ever be in that situation, but I'm just curious how that happens. Sounds like a bit of a legal hack. Did you mean with the 83b form?
From the perspective of the company, it is like reverse vesting.
Talk to a lawyer for the myriad details but if you ever hire someone who knows his stuff, he will want to exercise his options immediately.
It's obviously important to keep in mind that to exercise your options you'll need some cash. If your share is big and the company has been well funded already, you might need a lot of cash. And you need to be prepared to lose it all if the company fails.