Buffy and Spike have sex for the first time since "As You Were", being their first time after he got his soul ("Grave"). The two were last seen together as so in Buffy's imagination in Last Gleaming, and had they slept together in "Chosen".
Spike admits to himself being "afraid of falling asleep 'cause [Buffy] might not be here when you wake". Buffy herself had suffered of such situation with Angel ("Innocence") and Parer ("The Harsh Light of Day"). Riley was the first to be on her side ("The I in Team"), followed by Spike ("Wrecked"), though still an evil creature and having a troublesome relationship with Buffy.
While Buffy is sleeping, Spike says "Nothin' could ruin this", reminiscent to Buffy and Angel's dialog in bedroom in "I Will Remember You".
Spike's nightmare in which he feeds on a couple is reminiscent of Angel's nightmares in "Somnambulist". Both ensouled and working on the good side, they are haunted by visions of been turning back to their latent evil, sadistic and bloodthirsty selves.