I thought it was kinda corny, I mean I agree with IGN's review that it was easily the most "sitcom-y" of this season's episodes. Barney's loss of confidence was great, but Heidi Klum coming out of nowhere to give him assistance just seemed ridiculous.
I mean, the whole story of Marshall having a hardass trainer could just as easily have been applied to Ross from Friends or Kramer from Seinfeld with the same results... the payoff of Lily's trainer, who wasn't affiliated with the gym in any way was hilarious, though.
I'd give it a 6/10. This show is capable of so much better.
On another note, I threw in a salute to "Major Pain in the ass" yesterday at work. Everyone looked at me like I was ******ed. They'll understand one day.