>>All I know is my own experience. When I filed my taxes in 1999, I had earned some income in the US for which I paid taxes in the US. Because I passed the physical presence text for the income that I earned in the UK, I only paid taxes for that income in the UK.

Right. You had to pay UK tax because you passed the domicile test. However, as a US citizen you're again exposed to US tax on earned income above a threshold, and on any other non-earned income regardless of amount. I agree that until quite recently, the IRS had few mechanisms to check up on citizens abroad to extract its pound of flesh and hardly ever did it except for real delinquents hoarding their millions in Switzerland. But now the IRS has the cooperation of foreign banks to pursue citizen obligations down to the last dollar.

AFAICS tax on unearned income like pensions is what causes the most dismay, because there's no threshold. So a pensioner who married a Brit and lived in Coventry rather than Arkansas ;-) and qualifies for a modest UK pension, now is dismayed to discover that her pension is unearned income that is subject to US tax because she's still a US citizen.

>>Let's get rid of all these complicated tax laws and put the IRS out of business ;)

Heartily agree with the first (if you have time, check out the NZ-US tax treaty) but who will pay for your Medicare healthcare without the IRS? ;-)