I've had numerous discussions with people about 60Hz vs 120Hz, including one where a friend cited some study (sorry no link) which claimed that, perceptually, people couldn't tell the difference between these two refresh rates. I was incredulous. I'd been playing Quake at a high level for a number of years and anything lower than a v-sync'd 120Hz setup was painful, on the flip-side, playing 120fps@120Hz (CRT) felt so fluid, like water (hard to describe, you have to play on the two setups to feel it).

I haven't had the same experience on any flat panel display I've used till now but I'm on the lookout for a good 120Hz LCD gaming monitor in the hope I get the same experience again.