6.5/10. Basically "Brick Joke: The Episode!", this one gets point for being structurally audacious, but loses many more for not being all that funny. Taking a bunch of stock sitcom beats and putting them into a timeline-blending format gooses the proceedings a bit, but stories like Ted and Robin disagreeing about assertiveness, or Marshall working too much while Lily feels overwhelmed, or Barney trying to sleep with a black widow type just lead to more of the same, even if hearing the punchline before the setup of a joke is an entertaining exercise. That's basically what this is, an episode where you spend way more time saying, "that's pretty neat" than actually laughing at the jokes or being engaged with the story. Martin Short goes a little broad even for late-season HIMYM and Chris Elliott is starting to become as exhausting to the audience as he is to Marshall and Lily, but for the most part this is an average episode that deserves some credit for the difficulty of trick, but has little to offer beyond it.
(As an aside, it's hard not to compare this episode to Community's seminal episode "Remedial Chaos Theory," which aired in the same season, and makes this episode seem wanting and even unadventurous by comparison.)