The shortest answer: If the story is done well, I don't mind at all. Whether it's superego or write-what-you-know depends on how it's done, on the purpose for which the method is used, and on the author her/himself.
How do you feel about fictional characters who are obviously closely based on the author? Is this an example of authorial superego? Or just a natural extension of the "write what you know" advice?
The Bell Jar is a good example - I didn't feel that the thinly veiled autobiographical nature of the novel took away from the experience of reading it (granted, it has been many years since I've picked it up and read it all the way through). The novel itself certainly had a few structural shortcomings, and one could argue that this might have been due to its strongly autobiographical nature - our lives don't exactly follow any sort of nice narrative flow, complete with measured character and plot development, climax, and resolution. In a sense, that's where much of the fiction would have to come in. The author should know when to deviate from her/his own autobiographical feed in order to move the plot or allow for character development.
Copping to autobiographical characters or elements in one's own writing might be too close for comfort for some - writers already are baring much of their inner world by writing and sharing fiction; to admit to a specific character or plot line as being close to one's self or history might just be too uncomfortable, which could perhaps be an alternative explanation for Eugenides reluctance to claim Milton in The Marriage Plot as mostly instead of loosely based on himself. Perhaps today's culture would view such work as too egotistical and not fictional enough - I honestly don't know. Vonnegut's Slaughterhouse Five clearly contains experiences based on his own time in a POW camp in Dresden, and it's definitely his most well-known work and considered by many to be his best.
As an author of fiction that can seem remotely plausible or realistic, is it even possible to write without writing what you know, or at least, what you believe to be true on some deeper level? If you don't know from your own experience, you'd have to research to fill in the gaps of your own knowledge and experience. Either way, your fictional work would have to contain elements of what's known in order to be taken seriously at all.
What do you think?