Birdman, your post started off pretty strong, but towards the end it seemed you were more critical of Knapp & others as opposed to "fairly evaluating" Vick.
But I would say I agree with the majority of what Birdman said. Vick does those things from time to time. We can go back and forth about how often he does them, and which players, coaches, or positions "conspire" against him to do them rarely, but I'll just point out the key areas where I think is what holds Vick back the most from being a consistent, accurate, top-ranked passer.
And a lot of what I have to say was mentioned by dirty. And these are in no particular order...
1. Vick's Management of the Pocket
In watching tape of Vick, there is a rare occassion when he actually steps up in the pocket, like most QBs do. Instead, when he feels pressure, he usually immediately looks to evade that pressure laterally as opposed to vertically. As dirty said, sometimes this leads him to run right into an opposing defender, particularly a DE rushing from the edge (e.g. watch the Saints games). Well frankly, the pocket as Paul Brown created it is a vertical structure crafted to provide protection for the QB in front and to his sides, and with the gaps between the O-linemen are essentially throwing lanes for the QB to throw to. Thus, why stepping up in the pocket is preferred, because usually the QB steps up into one of these already available throwing lanes and thus gets an even clearer view downfield. Instead, when Vick "side-steps", he is typically side-stepping right where an OL is or DL is being blocked.
So what you're going to see a lot when you look at the tape is Vick turning to run, but then he has to turn again because the space he was headed to is now occupied by a OL or DL. At this point, his eyes have ceased being downfield. And the key to stepping up in the pocket is that a QB's eyes remain downfield. Once Vick makes that second direction change, he's no longer looking downfield and is instead focused on the pass rush. This is going to lead to a greater number of sacks simply because instead of focusing on getting rid of the ball, he's focused on holding it now.
Now, one of the many causes of this behavior is Vick's natural tendency and comfort zone from throwing and surveying the field from outside the pocket. He's a mobile and athletic QB that is used to throwing on the run. A more "traditional" pocket passer (which is the majority of QBs in the NFL) lacks this comfort zone, and when they begin to scramble, they look lost, make poor decisons, bad throws, etc.
So when Vick is side-stepping, it's him trying to escape the pocket in order to find his comfort zone. You'll often see from examining the tape that when Vick makes the majority of his downfield throws, he's outside the pocket.
2. Vick's Progressions (Lazy & Inconsistent)
Ron Jaworski first pointed this out to me when he was talking about how well Vick played in the Steelers and Bengals games, in that Vick was comfortably going through his progressions in those games, and thus was making the right decisions and accurate throws.
Without being a part of the Falcons play-calling and knowing their playbook, I can't be 100% sure if in the games where Vick's performance has been subpar if he was not going through his progressions, but it seems to me that is the case.
It's not the sole cause, but I think one of the contributing factors for the decrease in catches for Justin Griffith and Warrick Dunn is Vick's inconsistency when going through his progressions, and rarely looking for the dump-off. Instead, a lot of what I saw on tape, particularly in the 2nd half ot he season, was Vick rolling out of the pocket and chucking the ball deep. Now this obviously doesn't mean that Dunn/Griffith were open on every one of these plays, but I think there are probably too many examples on tape of Vick forcing downfield or ill-advised throws instead of taking the 4-yard throw to the flat or shovel to the RB.
I've seen examples on tape of Vick abandoning his reads rather quickly, at the moment a passing lane begins to widen enough that he tries to run it, and often times that new running lane closes just as fast it opened.
He was an effective college QB because he didn't have a lot of progressions and reads to go through. 1, 2, then run. This is a similar instance for a lot of college passers, particularly ones that have top notch WRs on their teams (as Vick did with Andre Davis). College QBs either force a helluva lot more passes or run the ball a lot more than NFL QBs, and it has a lot to do with the progressions.
As Birdman said, we've seen him do good things. He has the arm to make all the throws. We've seen pinpoint accuracy from him. We've seen him thread the needle, lead receivers, throw passes that only his guys can make, make the plays with his feet (like 1st downs) that need to be made, and improvise his way out of impossible situations. But IMO, for all those positives, these 2 issues I outlined above probably are just as big negatives. These 2 issues IMO are the 2 biggest when it comes to why he's so inconsistent, or at least why his great games are so far in between.
IMO, it's up to the next head coach/offensive coordinator to either do his best to eliminate these flaws or design a system where tehy can be disguised and/or minimized. IMO, at this point in Vick's career, you'll have a lot better success going for the latter.