The biggest disappointment for me was that Spike wanted to learn about himself, his race, his beginning, but learned nothing and returned home with an abandoned egg who will probably be Spike's pet in the future. The teenagers didn't teach him anything, he didn't try to socialize with the adults or try to find youngsters like himself. Nothing was really learned at all.
Personally, I was hoping for some background on Twilight and Spike's relationship (and at one point it seemed like they might do that), but that didn't happen. Not a problem though.
