I don't get lag playing games, video etc but really intermittently big lag on pressing home button - apps take an age to appear and absolutely nothing to see other than live wallpaper, screen gradually re-draws. Not what I expected from such a 'fast' phone - HTC desire didn't struggle! Yes, I've turned off S-Voice double press thing and I've got issues with some motion controls.
According to the video here (
LINK) the international version just got an update that fixes this issue. The reviewer described a "re-draw lag" in going back to the homescreen that seems to have been addressed in samsungs update. In the video, he said this happened more when using the Deep Sea Live wallpaper and that with a static wallpaper is wasn't an issue. ...but after the update, he noticed almost no lag even with the deep sea wall paper.
I can only recommend things you may not want to change, but here it goes...
1) try using less widgets, or eliminating them 1 by 1 until you find the one or two that may be the culprit of your homescreen lag.
2) use a different wallpaper (simpler/darker the better). This will keep your CPU resources focused on the widgets over the backround. Oh and, darker was only suggested to improve battery life, so if that's not an issue i guess you can ignore that part.
other then that, double check to see that power save mode is not enabled when the redraw happens...this was the only time i saw the redraw and disabling the power save mode fixed it.