In April of 2007 I bought the original 5D. I thought "OK, how much better can it become?". Well, it became MUCH better. I could not resist.
I have made some shots at ISO 3200 in extremely low light, f/2.8 and 1/20s. I double check the EXIF and say "No, this is not possible!".
I always looked down to video. Until I was given the capability to shoot video with lenses like the 70-200 f/2.8 IS...
It is able of amazing video. But this is NOT a video-camera. The controls, due to its shape, are somewhat difficult to handle. You either need a third hand or a tripod. I often use a monopod, which is a very good compromise. Keep in mind that in order to get the best results with video, you have to focus manually. And here is where lenses like the 70-200 shine. You can zoom without losing focus, as with cheap lenses.
And it costs less than what the original 5D cost, 16 months after its introduction!