I tried out the iPlayer for the first time last night (at the time of writing) to watch the first episode of the new series of Doctor Who, which I had missed the beginning of due to having to put the children to bed. On going to the BBC website it was just three clicks - one to start "watch live", one to restart the current program and one to maximize the window. And there was negligible buffering time, and it was higher definition than standard definition TV! I was very impressed. It was a great episode too - most of the Dalek episodes suffer from massive unexplained plot holes, but this one was quite well thought out.
Some of the US networks have streaming sites, but they all have adverts, the quality is worse than standard definition TV and new shows usually aren't available for a day to a week after they air. Plus a year's basic cable subscription costs more than a year's UK TV license.
Not entirely a fair comparison because you're taxed for TV. You remember that USA TV is not subsidized, hence the adverts.
That being said, we're about to convert to a "whole house DVR" solution that allows simultaneous recording and playback of up to 6 channels. It costs a premium, but it's worth it.
Hence mentioning cost of a UK TV license (which is what funds the BBC - they aren't funded through the normal tax system) relative to the cost of a US cable TV subscription. It's cheaper here, plus there are no adverts on the BBC, plus the internet on-demand service is miles ahead.
In Italy we have the worst of both worlds: we pay for TV with taxes (100eur/year for family) and we have advertisement on it!
Then consider me officially 660 nm with envy :-)