This has to be the best season finale in all the series - right next to the season 8 finale. What puts this one slightly ahead of S. 8 finale though is a solid season before it, whereas S. 8 was one of the weaker seasons in all, despite having some of the best episodes throughout the series (Time Travelers, S. 8 premiere, finale, etc.) most of the episodes were weaker. I can't say the same for S. 4
The episodes generally were solid and your more standard HIMYM show - funny, engaging, fun, entertaining, etc.
It was just a strong season. Plus it was probably the last where you feel it being a younger, newer show.. somewhat of a Part 1 if it's to be split into segments. The later-half of the series sort of begins around S. 5 or 6 I'd say.
S. 5 they begin to grow up and mature a little more. Many are 30+ at that point.
Seasons 1-4 they're basically in their 20's.
And what a way to end the season and segment! It was an amazingly written episode. It pulled a lot of loose ends together and tied up earlier plots and you had a sense of completion for many of the earlier storylines and themes.
S. 6 starts somewhat anew. You move into deeper ground and territory.
It begins to prove itself a lot.
But this is one of those episodes I always return to. I have maybe 5-8 episodes that stand-out in my mind as critical, special, captivating episodes throughout the 200+ episodes - this is one of them.
Everything is right about the episode. The soundtracks featured, the storylines, the atmosphere, the subtle messages it passes off; the way you really began to root for Ted and see some growth and maturity unfolding (in all of them really), but the show continues being who and what it is: a network sitcom. Funny. Goofy.
It's these episodes every now and again that make the show worth returning to and re-watching again and again even years later.