[cateye]

Yes, this is exactly also my experience. But in both cases, Agile or Waterfall doesn't really makes any (form scientific perspective significant) difference.

I've also experienced clients that just can't judge an iteration without seeing the whole application working. Or that a client changes his mind after seeing each iteration which can be more painful then changing just the spec.

As I suggested in my blog post, the book "Making Software: What Really Works, and Why We Believe It", the chapter "Architecting: how much and when?" by Barry Boehm treats this specific subject really well.