My goto camera is still my 5D Mark II. As I primarily shoot landscape, I love Wide Angle on a Full Frame body.
That said, I do occasionally shoot animals and people running.
The 5D Mark II's AF system, while not as bad as the Internet would like you to believe, does show it's age.
I'm tempted to pair up the 7D with my 5D, to better help with action shots. Currently I can get one for $1500 which is well within my price range. I currently have a 40D as a spare, and I like it well enough, but I'm not as happy with it's AF performance either.
So will I notice a noticeable improvement in AF for moving subjects, worthy of the investment, or should I make do with my 5D2, given than I use it more than any other body.