I'm thinking about changing from the 30d to the 40d myself and the post from pxl8 has just put another nail in the 30d coffin.
Andrew i've read somewhere that the claimed 6.5 fps is not achievable i don't know if anyone else has come across this as it's one of the 40d main selling points.
Review on DP Review states more like 6fps. I have access to a 40D and it is not far short of a 1DII. It's still quick for those bird take off moments
Using AI Servo at f/7.1 and f/5.6 (the cross type AF points work at f/5.6).
Good.
30D body for sale