I think that is very impressive performance for 1600 ISO. It is my understanding that the senor in the 40D is not the same one in the 400D, given that it's 14bit.
That was one of the reasons why I decided to upgrade to the 40D instead of the 400D. Although, I must admit that my 40D's sensor cleaning function doesn't do much and now it has ER99'd on me about ten times today.
I was thinking that I should not buy one of the first batches of 40Ds, that I should wait until next year. I don't think I'll make that mistake again. I hope my replacement 40D is a winner, otherwise, I'll not have another.
Congrats on some very fine performance. Your image is certainly usable, and IMHO, better than usable. Back in the days when I only shot film, I happily presented shots like that when I had low light or just plain needed the speed to give me some elbow room.
Best,
Michael