Same story here. Left in 2007, and no longer have any desire to return. My last visit, in 2010, left quite a bad taste in my mouth, with the creeping totalitarianism on display at the airports in particular. Welcome to America: don't forget that WE ARE ALWAYS WATCHING YOU.
What's especially depressing is that the commitment to paranoia and the dismantling of due process, civil rights, etc., is 100% bipartisan; there are no serious political voices taking a stand against it. Bush was of course bad; Obama -- my last great hope -- has extended and amplified everything that Bush did. And Obama's opponents are essentially unified in their position that Obama's chief failure has been to not dismantle due process and civil rights quickly enough. At this point, I think that Obama is probably still the lesser evil, but that's too damned evil for me to vote for.
I don't see any prospects for this reversing itself. Carry this trend out another decade or two, and it means the end of the American republic. There's nothing extraordinary about this thought: over long enough timeframes, great nations collapse all the time, and this is more or less the blueprint they follow when they do it: increasing paranoia about being beset by enemies both external and domestic; dismantling of internal political apparatus and centralisation of political power with a single individual; increasing inability to balance a budget, tolerate dissent, maintain infrastructure, etc. I fear that the present era will be remembered alongside Rome in the late 4th century, Spain in the early 1930s, etc.
I hope I'm wrong, and that those who stay can somehow turn it around. But at this point I'm glad I left.