I still fail to see the point in displaying ads right from the start. It will make you what, a nickel over a course of a month?
Not having ads could be a good selling point to visitors when starting out. When the time comes to have ads, you slowly introduce them little by little. I personally plan on only have ads when site is very busy and they will only be text ads.
Ok, I don't think that you should start displaying ads from day 1. But I don't think that you should wait too long, either. You want your visitors to have a reasonable expectation. Your site provides good information, but your site also runs ads to support itself.