Lag always exists. No such thing as zero lag. And it's bigger now than it used to be (thank you, HD generation).
But unless you're a seriously twitch-obsessed frame counter who plays fighting games and shmups at a very high level, you shouldn't notice a thing. If you aren't one of those types of gamers and you are noticing lag of some kind, then something else might be going on and you may want to start troubleshooting. The culprit could be any number of things, some fixable and others not.
Anyway, I just got a replacement AVR for my gaming setup from Onkyo after mangling the HDMI-out jack on the old one. No unusual lag issues with my old one (605) or my new one (509).
PSN & XBL ID: drop me a private message