A fascinating article by American professor Lynne Murphy (Senior Lecturer in Linguistics and English Language at the University of Sussex - my old university) who look at a series of studies about the attitude towards the English accent in America (h/t Andrew Sullivan):
The main significant effect found in this study was that people who'd lived at least three months outside the US rated the English accent significantly lower than people who'd only lived in the US. In fact, Americans who had not lived abroad considered the English-accented person to be much more intelligent than themselves, but the people who had lived abroad rated the standard American accent more intelligent than the standard English one. My preferred way of interpreting this (a bit tongue-in-cheek) is that Americans are happy to rate the English as more intelligent than themselves up until they actually start meeting and talking to the English.
I have found that having an English accent in America can be extremely useful at times, but frustrating at others. Generally, I seem to be regarded as being more intelligent and more important than I actually am (often a good thing), but conversely I would like to have genuine interactions with people rather than superficial ones based on things like my accent. Los Angeles is a particularly superficial town, so I can often get away with absolute murder (free tickets to events, guest lists, the attention of the opposite sex etc...), but as I get older, it gets less and less interesting. Most of my American friends have travelled extensively so are completely uninterested in my accent - and given my somewhat vain personality traits, this is probably a good thing.