I can usually get past a slowish beginning, but it definitely helps when it's immediately gripping. Interesting characters really help too.
Interesting point about being in just one character's head per book.... I tend *not* to read chapter titles for some reason, and it really takes me a few minutes to get the hang of books that switch pov with different characters, and indicate it by the chapter titles. I don't mind books like that, but I really like being with one character too.