The Canon EOS-40D is a camera that will appeal to a vast range of photographers from advanced amateurs to working photojournalists and wedding photographers. All will appreciate its exceptional image quality, ease of operation, speed, modest weight and size, compatibility with the vast Canon system and very reasonable price. [Canon 40D White Paper] I agree.
The 30D already sees a lot of professional use - The 40D offers enough improvements over the 30D to make an upgrade justifiable. Watch for them at the next wedding or other event you attend. And no less important will be the huge number of family memories preserved with the 40D.
With its all-around good performance combined with the densest Canon DSLR sensor available, the 40D will have a large number of wildlife (especially bird) photographers as its owners. I’ll personally be making the 40D part of my kit (replacing my 30D).