I think the line was actually “Our marriage isn’t on a piece of bark, it’s inside us.” I’m not sure there was any intended political commentary (if there was, it turned out to be very timely with Prop 8 passing only days earlier), but it was cool that for once, Marge talked Homer out of making some ridiculous and dangerous gesture to prove his love, because it wasn’t necessary in the first place. That runs counter to a lot of “Homer does something nuts to win Marge back” plots from recent years.
This isn’t particularly a standout episode and I always get nervous when they start monkeying with the past, but in this case (since they’ve established Ned as being 20 years older than Homer) it worked out pretty well. I forget how they originally were supposed to have met, and the original is probably better. Still…
Aside from that I did like the Bart and Lisa side gags. And “I wish I’d never met you…! or you…”