How Much Do I Have To Like Him/Her?

How much impact does the likability of the main character have on your overall enjoyment of a novel?

This has been front and center for me since attending a discussion about Ann Patchett's "State of Wonder" (2011) a few weeks ago. But the discussion was only the catalyst for my question; some form of it has been rumbling around in my head a long time. I'd really like to hear your response to this.

Let me grease your wheels a bit. Think of the last novel that really got to you - one that you've recommended to others. How likable was the central character? In my experience, distasteful central characters often sour people on a book. If you share my experience, what do you suppose accounts for this? If you don't, please recommend a book you've loved where the main character is despicable. I want to read more of those, not because I revel in depravity, but because I'm confident authors able to pull this off are among our most skilled.

My wife recently finished John Updike's four "Rabbit" novels. Unlike me, she read them in order; it was such fun discussing the foibles of Updike's most famous and feckless character as he aged through the series. Rabbit never rose to the level of likability. I don't believe it's an accident Updike is revered as an author. What do you think?