YouGamers published an interview with 3D Realms' Scott Miller, here's a snip:
Scott: First, we fully admit we’re screwed up the development of DNF, and it’s now an industry joke. I laugh (and cry) when I think about it, too. Our fault is that we set the bar too high, and we tried too hard to make the game to beat all games. In the last 18 months we’ve taken a much more realistic look at the project, we’ve hired a truckload of experienced help, and I personally believe we are now on the right track…finally.
Full article with screenshots (not of DNF of course..) over here.