The most complex part of a web-based service startup is the development process. You have to figure out the UI, among other things... While most people believe the UI will "make or break" a service, that simply isn't true most of the time. Craigslist is ugly, no question about that... But it's successful because it services a real need. On the other hand, a site with an overly complex UI can scare users away. I really like to consider the UI to be a form of art (and as we all know, forms of art can be ugly yet in demand). I like a service that has both a simple and good looking UI, while meeting a real consumer demand - Hopefully we are doing just that.
The development period is also like the "quiet period"... You build, you test, you build, you test, you tweak, you build. The "testing" and the "tweaking" are the vocal aspects where other members input their thoughts. The rest of the time, it's just keyboards punching in code.
A little stressful? Yes... But that's what a startup is all about.