Great episode: up and down ride with some touching moments and a lot of tension that leads into the "true" finale. I have to say that it was a great episode, but then no Chuck episode has been terrible or even mediocre. But, there is that sense when you're watching it that an era is about to come to an end... a great TV show that deserves 5 more years is ending and TV just gets that much worse after it is all said and done.
The only real downside outside of the emotional issues regarding it ending is that it is mostly a lead up to the next episode and thus most it is all tension with little resolution, so as a stand alone episode it isn't the greatest. Taken as a whole instead of just a part of a 2 episode finale, it works. Just by itself, clearly it won't. No surprise there though.