The good episodes start at #6 with "Our Mrs Reynolds" and continues right through to 11/12 ("Trash"/"The Message"- some like "The Message" and some don't). "Heart of Gold" is hit-and-miss with some great moments but some stock cliches too. "Objects in Space" is absolutely excellent.
Some non-spoilery spoilers to keep you interested:
Our Mrs. Reyonds- "You're good." "You're amazing
... who are you?"
Jaynestown- the bartender slapping the bottle out of Jayne's gaping maw. Simon finding an appropriate time to swear. Book's hair.
Out of Gas- Kaylee getting hired by Mal.
Ariel- the whole episode, particularly Simon getting a chance to do what he does best. Beware though- this episode has one very gory scene in it.
War Stories- Wash and Mal's conversation about Mal's feelings towards Zoe. "Screw you!" "Get in line!"
Trash- "Is there anybody there...? Anybody else?"
The Message- The way the actual message is used throughout the episode and how it ties in to the end.
Objects in Space- "I'm not on the ship. I'm in the ship. I am the ship."