It picks up once they stop with the cutscene-every-3-minutes bullsh*t.
If you've played MGS1 then it's well seeing all of Act 4 at least, and if you get that far it's only about 40 minutes more gameplay before you get to the ending.
Despite what I earlier said, i'm still waiting for my subscription to go through, as I find it quite annoying when I try to debate something and get told i've already posted 3 times.