Its pretty easy to cite examples of a corner getting burned when he is playing injured. From my vantage point, Henry was only getting exploited towards the end of the year when he was having issues with his knee. You could see him limping off the field a few times on pass plays. I speak from experience when I say this, but when nursing an injury such as his, you put yourself in the position to make the play, safely.
I am quite happy with the CB's we have now. Aaron Glenn makes a great compliment to the two, bringing his years of experience to the plate. Newman, while smaller, matches up well against speedier receivers. Henry is more physical, and matches up well against the larger recievers. If you remember the Giants games from last year, Henry was matched up on Burress, and did a great job harassing him and pretty much taking him away from Manning as an option. Even this year, when Newman was matched up on Burress, and having trouble, I felt much more relieved to see him matched up on Henry the rest of the game. Thats not to say I'd like to see some youth in the CB's...
He is legit, he is most likely not going anywhere, deal with it.