Interesting discussion.
If you read
THIS thread you would get a totally different opinion.
My experience with the 500D has been mixed. Sometimes the pics are so noisy, I just can't use them. Here is one I was really disappointed with. Click on the image to zoom in and you will see what I mean.
http://deepspaceplace.com/show.php?id=ngc1976b
I have a few hunches what's going on, but I don't have the evidence to back it up. One day if I have the time and energy, I'll look into it again.
James