I'm reviving this thread because I do notice this too, you aren't lying. It's a problem that resides in the monitor itself, not the drivers or cable or anything else. Very few LCDs don't have this problem, and I'm looking around for ones that don't have input lag (obviously). And actually I didn't see this lag until I switched to an old 17" crt and I noticed the mouse was moving faster or something, then I realized what had been happening: the cursor was updating its position on time with my actual hand movements, instead of lagging 20+ ms behind with my LCD.
If anyone (who can point out input lag if they see it) knows of any LCD panels that don't have input lag, tell me, I want to know which ones don't.