Generally, you watch Glee! for the musical numbers, not the plot. The show works best when the characters and subplots drive the musical numbers, and this is a perfect example. Will is thinking about asking Emma to marry him, and asks the glee club members to come up with songs that will serve as a proposal. All their suggestions are great. One of them features a rarity on Glee!: Singers in harmony. "The First Time Ever I Saw Your Face" was better than Roberta Flack's original.
Romance is in the air, and the characters are set in motion.
The show opens with the cast doing a pretty good version of "Summer Nights" from Grease, about a summer romance between two of the characters, one of whom wants to continue.
The poignant moments are from Becky, the character with Down's Syndrome. She has an inner voice (Helen Mirren) who decides which guy she wants. That plays out with a verisimilitude that Glee! only occasionally achieves.
I won't spoil the ending(s), but all of the subplots reach decision points, and all of them work wonderfully.
I don't watch Glee! for internal consistency, and a show about High School kids now in it's third year is already stretching my belief suspenders. Still, a show worth watching, even if I have to wade through a bunch of mediocre soap opera to get to the good stuff.