"Out of Gas" is a fantastic episode I mean it's got some great scenes in it, the music and scene of Mal walking his way from the cago bay/catwalks up to bridge/cockpit is just beautiful. This is just one of those episodes that is nearly perfection.
The next episode, Ariel, is another fan-favorite too and one of the show's top episodes it also gives you a sense of what many of the episodes of the series would've been like as it's one of the two "caper" episodes in the series as it is now.
It's also interesting to note that the salesman saying "treat this ship, proper", etc isn't even talking about what will become Serenity
. That's the beauty of the "structure" of the episode as we learn that through it we're learning how various members of the crew came to be on the ship. So when we get to the final scene it's a bit surprising and actually makes sense that Mal fell in love with Serenity
at first sight and it wasn't even the ship he was trying to be sold.