I have a lot of stuff in my life to take care of already. If launching a product means more problems and little extra money, I definitely procrastinate.
Here are just a few problems I worry about before launch (just off the top of my head):
1) Connection problems that aren't even something I can personally fix (client-side)
2) Feature requests. Tweak requests. People that don't understand that the app isn't a CUSTOM program and wonder why they can't get what they want even though they are paying for it.
3) Credit card payment processing problems. Denied cards, expired cards, overdraft cards, PayPal, Auth.net, 2co, etc. The problem of what to do with accounts when someone isn't paying or when someone says they are trying to pay, or will pay, but don't pay... blah blah blah. PROBLEMS!!!
4) Meetings and Training. The app can be STUPID SIMPLE, but there are still those corporate people that want a training session, or a conference call, white papers, or a live meeting to discuss the benefits of our app. Seriously. Pay $20-$100 and just find out. If you are thinking about my app that much, it's probably not for you.
4) Monitoring backups, restores, server problems, data center problems, storage space, vps, dedicated servers, s3, e3, cloud, load problems, twitter api, facebook connect, etc, etc, etc
Problems, problems, problems, problems.
Maybe this isn't an issue when you have VC, but in the bootstrapping world, failure doesn't matter as much as PROBLEMS do.