I can't just accept claims as truth without an explanation of how it works. As I've already said, all the explanations I've been able to find use phrases like "lagless illusion" and "latency hiding". These are just PR explanations and do nothing to make us understand the details of how this technique works. If it truly does reduce latency, then why doesn't it say so in the official explanation? It makes me very suspicious.
The way I understand it is that GGPO simply displays what happens locally before syncronizing with the opponent. If later, the outcome of the sync confirms what has already been displayed, then all is good. However, if the sync invalidates what has already been displayed, a rollback will occur back to that point. This will in effect "rewind" what is being displayed on the screen and continue on from a few moments before, but with a different outcome.
Note that the above is just how I interpret the official explanation and might not be correct, but let's say that I am: This will make your own moves come out with no input lag as if playing offline, making combos and especially just frames easier (just like Windie said). But your opponent's actions will still be affected by latency, making reacting to lows and punishing fast moves just as hard/impossible as usual.
