Got mine shortly after I retired in Dec.09. It was/is such a huge step up from the 40D. If you have half as much fun with your MK IV as I've had with mine you are in for a really good time. I am not a professional but I am serious, especially about eagles.
Read the manual, and learn the camera. Often many of the so called short comings are user error.
There are some that this camera doesn't work for, and I would never say for them it is not right. Some are remarkable photographers and have found the MK IV to be lacking. That is not my experience.
Hope it turns out to be worth every penny you've invested in it.
BTW if you get into birds and BIFs might as well jump to the 500mmf4L.....bottomless pit this birding/BIF thing is