Through a series of events my first camera-related purchase of 2014 turned out to be a 5D Mark II. After having spent a little time with it, my thoughts as follows in no specific order.
It is arguably the best camera I have ever held. No, I have not held many of them, and despite its shortcomings, it's such a serious step up from the 40D that there is no question about it.
It is very difficult to quantify the difference between full-frame and crop-sensor. (Other than the size being the most obvious.) I could have spent less and gotten a camera with about the same amount of megapixels. High-ISO performance of modern crop-sensor cameras is almost on the same level as the 5D2. I do believe, however, that there is a subtle difference in the overall look of an image between different sensor/film sizes.
The famed auto-focus of the 5D2 has not caused me any trouble just yet (though the smaller depth of field does require more care, which is something I need to improve). Most likely due to the fact that I am only using the center point, something that has hung on all the way from using the 1000D.
So far, it has performed well. It will be interesting to see when the first real post-processing comes around.
As an addendum, I also noticed that all my digital cameras come from roughly the same time period: my Ixus 960 IS from 2007, 1000D from 2008, 40D from 2007, and 5D2 from 2008...