Personally, we've been self-funding Openomy (http://www.openomy.com) since it began in mid-2005. Overall, I wouldn't change a thing. We now have 50K+ users, a scalable infrastructure, and full control over what happens with the site.

That said, I think we hurt ourselves by not looking to take _any_ capital: we spent a lot of time rearchitecting our infrastructure to scale, and we still work on the project only on the side. If we could have hired a couple engineers and worked full-time, I think we could be much further along in completing our vision. We may have even been able to do more marketing (more == any)! ;)

Still, to note just how cheap it is to do a project like this these days, we spend <$1000/month on our servers (colocation/bandwidth + S3), and $0/month on anything else.

I'd love to hear from others and to see how bootstrapping/self-funding has treated you, what you enjoy the most, what the hardest part is, etc.