What does it mean to say that those in heaven see the punishment of the wicked? Admittedly, it is disturbing to us to think of those in heaven triumphing over those in hell as they are in conscious, eternal torment (just ask someone--Christian or non-Christian--what they think the most off-putting part of Christianity is and see if they don't say the doctrine of eternal punishment). Augustine suggests that it's not so much that the redeemed in heaven actually see the punishment of the reprobate, as it is that they know that it's going on and admit the justice of it.
If anything, Augustine is a bit light here. I think it's probably better to say that the saints in heaven will see with refined sight. That is, one of the reasons we struggle with the idea of non-Christians spending eternity in hell is that we have too light a view of sin. We tend to think that it's not so bad, and that the idea of eternal punishment must be overkill. When we remember that it is rebellion against a perfectly holy and infinite God it's easier to see the true desserts of our moral wickedness. And of course as believers we see this every time we look at the cross--that is what we deserved, and what all who reject Christ will receive.
Augustine says that if you want to know more about the Antichrist as explored in Daniel, you should read Jerome's commentary (part of which is found here). Jerome was responding to Porphyry, who had argued that Daniel was actually a later author writing during the Maccabean period anachronistically (much like the contemporary historical critical school would argue) rather than during the Persian period prophetically. Augustine's point is that Daniel is in line with other apocalyptic writings of Scripture.