I was disappointed with how the green dress story came to be. The whole points system between Ted and Barney was really contrived from the get-go. (Why were they even keeping points in the first place??) I think the writers could have done a littler more with Barney and Lily in this episode. After all, around this time Lily is supposed to be having some pregnancy body issues. Just that fact that there wasn't even a slight nod to that shows that the writers were completely lost and just crapped this storyline out at the eleventh hour.
With that said, I always liked those moments of "but we'll get to that later." Maybe because I'm starting to heartily dislike the show, but they have always given me something to look forward to and a reason to keep watching. I can't believe I'm saying this, but even when the explanation is an obvious last-minute throw-together, I still feel that nostalgia and connection that I've felt in a few episodes way back when. I admired the way the writers have kept true to how a father would talk to his kids: such as "eating sandwiches", glossing over some of the sexual parts, and saying, "But we'll get to that later."
That's why I'm just trying to appreciate the show as a whole and covering my ears and singing during the bad parts. HIMYM has too good a concept for me to just criticize and abandon because of downhill script writing.
As for the times when the pay-off was pretty good: the goat storyline. What I liked most about how Future Ted brought up the goat is that it wasn't so much about "How the f- is there a goat in the bathroom?" as it was "What is going to happen between Robin and Ted that will result in Robin living with him next year?" In that sense, you didn't really care about the "pay-off" because you just wanted to know "why" not "how".
So, back with the green dress, I think it's better if we go back to that "Mermaid Theory" episode and realize that the whole bit with the allusion to the future was for the sake of showing us that in the near future, Lily will finally get pregnant--not so much that Ted will be wearing a dress. In that sense, the green dress bit would have gone down earlier in the pregnancy (or I guess earlier in the third trimester).