Don't finalize the logo before you come up with a business plan that works.
Don't spend a lot of time thinking about your vacation policy before you have a product that people actually want to buy.
There are endless small details to get right before you have something that you're truly proud of. No doubt about it. But there are frightening and huge holes in any bridge to the future, and until you figure out how to get across, I'm not sure it matters if you have a typo on page 4.
Good points from Seth Godin on what questions to ask first.