I agree on 20-30 hours estimate but in general, you just cannot sit down in a few days straight and find out all competitors. The reason is very simple: most of

I agree on 20-30 hours estimate but in general, you just cannot sit down in a few days straight and find out all competitors. The reason is very simple: most of the time, you don't know the right keyword to search. This happened to me. I spent days searching for competitors. Then I thought I had a pretty good idea and started on coding. During that time, my head started to pop out with "alternative" keywords, not necessarily direct competitor keywords. Those are dangerous because again, most of the time, people already have a way to do certain things (i.e. alternative solution). So that 20-30 hours is just the tip of the iceberg. After you start reading blogs and talking to people, what you ended up having is a way better list of keywords to search for. By the way, don't forget to get ideas from Google Keyword Tool itself.