Spoilers and lots of them!
This is safe to read if you've finished reading Chapters Four and Five... but please don't read this if you haven't. They are both such wonderful chapters and I'd hate to ruin them for you.
Chapter Four: The Seven Potters
General comment: Rowling doesn't mess around. It's only chapter four and she already has a major battle scene featuring Voldemort. Talk about hitting the ground running (or flying, as it were.)
-Hedwig dying so quickly and unexpectedly.
-A solid brick wall appearing out of nowhere in midair.
-The helplessness that Harry experienced being with Hagrid who was the least talented wizard.
-The sidecar falling to earth.
-Shock that the Death Eaters figured out who the real Harry was.
-The terror of Voldemort catching up with Harry so soon.
Funny: The reactions of the characters who changed into Harry, and the image of each of them lining up to take a rucksack and an owl cage. I particularly liked Harry's comment that the doubles were being rather immodest with his body.
Connection to previous books: Hagrid does have Sirius' bike! I knew it! I'm glad Rowling brought it back. Also, Fred's comments about Mad Eye not being able to tell the twins apart is a mirror of Fred's conversation with Mrs. Weasley in Book 1 in the train station (Sorcerer's Stone, Scholastic hardcover, pg. 92).
Favorite quote: There were so many funny lines in the beginning of this chapter that it's hard to chose. I thought everything Fred and George said was hysterical. But if I had to pick just one, it would be after everyone has drunk the Polyjuice potion:
"Fred and George turned to each other and said together, 'Wow- we're identical!'
'I dunno, though, I think I'm still better looking,' said Fred." (Scholastic hardcover, pg. 51)
Chapter Five: Fallen Warrior
General comment: This was a fantastic and suspenseful chapter. It really kept me on the edge of my seat. Since it was the last book, I felt that really anyone could die... that no one was safe. I thought it was wonderful the way Rowling staggered the arrival times at the Burrow to leave the reader in suspense as long as possible.
-The psych-out that Hagrid was dead. That was gut-wrenching.
-Harry's reaction to Andromeda Tonks.
-Lupin telling Harry that the time to disarm was past, now was the time to kill.
-Mr. Weasley's angry insistence to see his injured son.
-Mad Eye's death, because I always saw him as such a tough character.
-Bill's salute to Mad Eye which was done so quickly out of necessity.
-Fleur's allegiance to the Order of the Phoenix... it's the first time I really saw that.
-Harry trying to be an adult and proclaiming that he trusts everyone in the room.
Funny: Fred and George again, of course. I loved that George had a sense of humor even in light of a significant injury. I also liked the sight gag of Hagrid continually getting stuck in doorways.
Favorite quote: Fred's comment after George says that he's holey.
"Pathetic," he told George. "Pathetic! With the whole wide world of ear-related humor before you, you go for holey?" (Scholastic hardcover, pg. 75)