I have gone from a 30D (amazing camera), to a 5D, to a 50D, a 7D and now a 5D Mk II. The only one I wish I had not purchased is the 50D, only because it was too similar to the 30D. I have kept the 30D because I have an underwater case for it and don't want to spend another $1500 to make something else waterproof.
The 5D would still come out when I wanted to do anything like a portrait. You just can't beat the image quality of a full frame sensor camera when you are doing people shots. The 7D is still my "take it everywhere" camera. Best image quality while not needing to cary an external flash. That, and I am starting to get into video, so it has that going for it as well.
Just got the 5D Mk II yesterday. Mostly playing with the video to see if I can do anything at all interesting with it. Probably gonna head out and shoot stills today, weather permitting.
We are probably at least 3 months, and more like 9 months, from the introduction of the 5D Mk II's replacement. At least according to canonrumors.com. Price on the 5D Mk II finally got to the point where I didn't think the bruises would show from the beating I knew I would get from my wife. Besides, the savings account was just sitting there with all that money in it. I just had to do some retail therapy. lol
So, to answer the question, an original 5D and a 7D are different animals. The 7D adds video to your tool box, the 5D a major upgrade in still image quality. Not everyone sees the better quality, but you will. Since you can't please everyone else, might as well please yourself.