When Buffy opens the letter sent from UC Sunnydale, her address is wrong. It reads 1630 Crestview. Her actual address, which has been mentioned many times on the show, is 1630 Revello Drive.
Towards the end when Buffy is leaving Spike, you can first see her eyes in a closeup. They are dark brown. When she comes up the stairs she has light blue eyes.
The Doublemeat burger disappears and re-appears in Buffy's hand between shots.
When Sam says "We better regroup", you can see that her lips aren't moving (widescreen version only).
When Buffy and Riley enter the alley in search of the demon you can see the green filter on the left side of the screen from the 13:30 to 14:00 point.