Hi Rob. You do have a little noise to deal with. The 40D seem to have a much better signal to noise ratio when used at 800ISO but there are a few things you can do if you are going to use higher ISO figures. I hope you don't mind, I have taken a copy of your image and run it through Noiseware on the default setting. You can download a copy of NoisewareCE off the net free at
http://www.imagenomic.com/download.aspx Scroll to the bottom of the page. The standard version is very cheap and has more features.
I made no other changes to this image. Hope this helps.