Beautiful design is not a prerequisite for success
blog.dustincurtis.com
blog.dustincurtis.com
If you take a closer look, all of given examples have really polished up their design over time as they became more and more successful (well... except myspace that is).
I think that the super slick look can actually hurt an app.
www.gowalla.com comes to mind.
Enormous cuddly looking stuff makes it hard for me to know where I'm supposed to focus.