Valve caused quite a stir with the new netcode, as this rant on GameSurge outlines. It focuses mainly on CS, here's a slice:
However, the rant is a bit opinionated (of course) and he has his facts wrong. Anyway, thanks to hl.net for the info.A Low Pinger may completely unload 30 AK-47 rounds into a High Pinger's chest only to find out that he really only registered a few hits or none at all. This is because the position prediction and hit tally on the Low Ping client's machine is first checked against the server’s for validation, which may be different, and if so…discounted. Very frustrating indeed. This is best visualized by delayed Death sequences seen when a Low Ping Player Snipes a High Ping Player with the AWP.