The first time that I watched this episode, I hadn't seen the rest of the series (there was a conflict on the night/time that it aired, so we never watched it) so Cordy appearing didn't seem all that significant to me. After seeing the entire series, though, I have to say that I don't know how Season 5 could have worked the way that it did if Cordy had still been around, because she wouldn't have let Angel take over the Wolfram & Hart law offices in the first place. She might have even talked him out of what he did to Connor at the end of Season 4.The last episode with my favorite character from the Buffyverse. It was sad to see Cordelia leave the way she did, and while I did appreciate this episode, I felt Cordelia deserved more. I know pretty much everybody will agree with me that Cordelia should have been in season 5 and she needed to be beside Angel and the others in the final scene of "Not Fade Away".
Also, I seriously doubt that she would have allowed Spike to be there all Season without informing Buffy that he was back.