The most interesting part of this passage is what isn't written down. What was said between the angel and the seven thunders at the end of verse 3? I suspect that later in life, John would sit back and ponder what he heard, and wonder when God would see fit to reveal those words.
A little digging into some commentaries and it seems that speculation of what John heard is less important than the description that he was writing things down as they happened in his vision, rather than years afterward. This adds credibility to the accuracy of what is recorded. Also, by that same premise, that means John is "live tweeting" the event 2000 years before Twitter.