I have a Meike one for my 40D and i did a comparison with my bosses Canon one.There were 2 differences,1 being the texture of the rubber is slightly different and the only is the flap for the battery compartment is curve on the Canon one.
I personally don't like the feel of the 40D with a grip as i do think it's a big enough body on it's on (but i did come from a gripped 400D to 40D)