The lag is pretty much random depending on your hardware.
Just because yours doesn't lag, good for you, but it's really not helpful to say "ignore people who say it lags" or "upgrade your PC".
Sometimes it works fine on an average PC, sometimes it lags on a high end PC. I chop and change my hardware around every few days, always trying out new motherboards, CPU's etc. I have experienced unplayable lag (skt AM2 AMD X2 6000), slightly annoying lag (skt 939 AMD X2 4800), and no lag at all (Intel Q6600).
Adjusting the graphics settings or video/audio calibration won't help you much, when my set-up suffered from lag I spent ages trying to tweak it, with little or no improvement.
In my opinion the game is flawed as it will not function at a playable level on SOME PC's that are better than the recommended spec. Maybe another patch would fix this (v1.1 didn't).
My advice would be to take a chance and buy it anyway, and if it lags then send it back. If your PC meets the requirements and it still doesn't work, you're entitled to a refund.