briansquibb, one of the concerns I have with a 5D Mark II is that I would be giving up FPS. My 40D has 6.5 and the 5D has 3.9. I also prefer a cropped frame since I like to shoot zoomed in sports shots. Finally, I was worried that the ISO on the 5D would not live up to my expectations. My 40D ISO is awful at 1600. But as Mt Spokane Photography pointed out, I should keep my ISO below 800 on my 40D. This means I cannot get decent shots shooting outdoor soccer after 5:30 pm, this time of year .
However, I think I can compromise and keep my 40D as a backup for outdoor sports when shooting in bright sunlight and the 5D for sports shots where there is poor lighting conditions and where I don't need as much reach (i.e. inside a gym). I'm just waiting for this month's announcements before I make a final decision .
BTW, Mt Spokane Photography nice shot! I am glad to see that the 5D has good ISO performance.
As I see it you are shooting at the low end - say 100mm. On a 5DII you would be getting the same image with 160mm - which works with your zoom
At iso3200 you would be shooting at 2 stops faster than on the 40D so motion blur would disappear and background blur would improve at the same time
You will also be shooting at 21mps and getting better IQ
1fps reduction is not too critical for your sports - you should be able to anticipate when things are going to happen.
So what is the alternative? a 7D with all its issues or (relatively) low light performance.