So, when you say "sharpness" are you referring to how detail looks zoomed in closely or how the overall image looks when viewed "normally"?
I am positive that it is user error.
By sharpness I mean that when I zoom in on my pictures they are not sharp. With my 20D I kept saying that it was because of the shortness of megapixels, however I am seeing that with my 5D2 my images are still not very sharp when I zoom in on them.
What has me so confused is that before I bought the 5D2, I played with a Nikon D700 in a store. The guy behind the counter let me put my card in and keep the pictures that I took. These were incredibly sharp when I examined them closely. The best pictures that I have ever taken, and I only played with it for a few minutes. However, since I already owned a couple of Canon L series lenses, I stuck with Canon and bought the 5D2 expecting the same sharpness.
I am looking at all of you guys images on this site and look forward to the day that mine will look the same. However, if you are getting these results with the 5D2, I see no need to make any type of switch to Nikon. I'll just keep watching, reading and learning until I get it right.