Actually, if I recall, a lot of people thought the 5D2 fell well short of the 5D Classic when the newer model was first introduced. I wouldn't know, personally... I held off buying any full frame until there was some sort of dust control effort built in. It seems to me now that people have really learned how to optimize the files from the 5D2, and most are very happy with what it can produce (the 1Ds MkIV, when it appears, should be a real kick ass camera!)
"There are many people who think that the 7D can even rival the 5D Mark II at high ISO. However, make no mistake, after my testing I have to say that although the 7D is quite good at high ISO by itself, it is still no match compared to the 5D Mark II. The 5D Mark II has at least 1 stop advantage I would say at high ISO. Not only is the noise level less on the 5D Mark II, but detail retention is also noticeably better too. "
-- Roland Lim
Using the cameras alongside each other, I agree with this 100%.
I also feel the 5D2 still enjoys about one additional stop of usable high ISO performance (about 6400) compared to the 7D (about 3200). I only use full steps of ISO on both cameras, so it might be possible to eke out another 1/3 or 1/2 stop, one way or the other. And admittedly, my "testing" is far from very scienterrific... I just go shoot with the cameras with a variety of lenses and post process a lot of images. Using 50D a lot too, I'd put it about one stop further down the down the ladder (and the 40D along with it, no significant ISO performance diff. between 40 & 50D, but the 50D was still impressive considering the big increase in MP). For me, 50D's "usable" high ISO = 1600.
The AF of the 7D is a lot more responsive than the 5D2's. But the full framer is downright pokey compared to the 50D, too. I would guesstimate the FF camera takes roughly twice as long to find focus and simply doesn't track movement as well. The six hidden expansion points help it achieve whatever level of performance it does enjoy. I hate to think how the 5D2's AF would perform without those extra points (7D has expansion points, the 50D doesn't... I bet the 5D MKIII, when it appears, will have dual processors or a separate, dedicated AF processor).
But all that rich detail the 5D2 can deliver - like practically no other DSLR - makes the camera well worth putting up with some a few idiosyncracies, especially when doing certain, more deliberate and less frantic types of shooting. I like pairing up 1.6X format and 1X format cameras, too. This leverages one's lens kit nicely... (But I still found I wanted to add two or three lenses to my kit when I got the FF. 
)
Comparing the AF of the 7D to the 50D's AF, I really don't see a lot of difference... yet! But I've been using the 50D a lot longer and have figured out ways to make it's AF system do what I need it to do, with a high hit rate (read that as... most missed focus issues are "user error", not any fault of the camera).
Right out of the box the 7D's AF at least matches the 50D's. I suspect as I become more familiar with 7D and learn to tweak its AF system for a wide range of situations, it will work even better than 50D for me, which is saying a lot because I wasn't dissatisfied wih 50D AF at all. The 7D is a sports/news/BIF/moving target camera. I'd call it a 1D4 "lite". It's got a lot of other nice step-up features, besides ISO and AF performance. But the ISO and the AF are the main reaasons I am in the process of upgrading on a much faster schedule than I'd normally do. I really want to encourage Canon, for finally giving 1.6X some of the respect it deserves. They've been treating APS-C as a mid consumer/semi pro format, at best, in the past. The 7D is more of a pro/high end consumer camera, I think. Hope that makes sense!
I have commented elsewhere that I think the 7D is quite likely overkill for some people. In fact, anyone really new to using DSLR, I'd probably recommend a Rebel/xxxD or 50D instead of 7D. I can see where folks could get a bit lost in the added complexity and frustrated with the more sophisticated 7D, especially the AF system customizability. There's a real herd mentality stampeding toward the latest-and-greatest model right now. I suspect we'll be seeing some whining and complaints here soon, from folks who are simply in over their head with the 7D, would have been better served with Rebel or 50D. (I'm trying not to sound derogatory with this. For example, I think a 1D/1Ds would be a bit of an overkill for me and I've been shooting for 30+ years with a wide variety of cameras, a bit less than half of that time professionally.)
hopefully...
