Great movie! I especially liked how they reused Bill Melendez's old Snoopy and Woodstock vocal effects, along with giving the original Patty and Violent prominent appearances. I also liked it during the end when they showed Snoopy as the Flying Ace with his siblings (Spike, Belle, Olaf, Marbles and Andy.) It was very faithful to the comic strip and the TV specials.
When Lucy pulled the football away at the end, I jumped out of my seat and groaned! Having read a ton of the strips, there was some material that I knew was going to happen. The ending did remind me quite a bit of the ending to "You're in Love, Charlie Brown."
My only problems with it were the music (not enough Vince Guaraldi tunes, and a little too pop/contemporary-ish at times), and how they put Peppermint Patty, Marcie and Franklin in the same class as Charlie Brown, Linus, Lucy, etc. I thought those three were supposed to go to a different school!
Overall, it reminded me a lot of the Peanuts specials made since the early 2000s in some ways. Charles Schulz would have been proud...