I made a post not too long ago asking for opinions on a entry level dlrs camera. Many posters suggested either the Canon Rebel XT or the Nikon D40 for the budget I have. I went to Bestbuy and I was able to try both of them and now I'm on the fence. They are both good cameras and they feel real good in my hands. My only problem is which one I should go with? I'm worried about compatibility issues with OS X and will I have any problems upgrading the lens in the future?