Yes and no. Launching quickly can be an advantage. Bugs or slowness can be a disadvantage. Often times people don't have time to revisit a site. They check

Yes and no. Launching quickly can be an advantage. Bugs or slowness can be a disadvantage. Often times people don't have time to revisit a site. They check it out once, and if they don't like it they never come back. It's important not to overmarket your site.