For Spike, it gave him another chance to feel her, to know she was real.  With everything that had happened in the past few hours, his sense of reality was pretty messed up.  The Claim.  Damn him for doing that.  It was strong enough on a mortal, but for Angelus to do what he did... It was worse than rape, forcing open that claim again.  It was like a backdoor on a computer program, a way past all the defenses and the armor and Spike knew he was hideously vulnerable again.