I think the writers blew a chance to write a great episode around a pivotal plot point with this episode. The breaking up and reuniting of featured couples should be few and far between during a sitcom's life cycle. So when you're going to do it, do it right.
(Friends, though they did it a little too much, did it right. Look at the top rated episodes of Friends, and you'll see a lot of Ross/Rachel, Chandler/Monica hook up and break up episodes.)
The crazy eyes theme was gimmicky; that's the one thing that annoyed me about the plot. It was saved however, by the non-chronological explanation of Lilly stalking Marshall's new love interest. That was fun and well done. The reunion, however, was just a little too anti-climatic.
But the subplot just didn't do it for me at all. Barney gets called by the wrong name and this becomes the major vehicle for driving the comedic subplot of the show? That joke just got old early for me.
All-in-all I think they whiffed on the chance to write a milestone episode around Lilly and Marshall's reunion. It was watchable, but certainly not notable. Still this remains a solid show for me.