Deus Ex: Human Revolution mouse lag?

I've just installed DX:HR via Steam, and I've noticed there's really bad mouse/keyboard lag in the game. Framerate seems fine for the most part, but when I move the mouse, there's about a quarter or half-second delay before my aim moves. It's making the game almost unplayable -- I just had to struggle for a second or two to open a vent because I kept overcorrecting.

Does anybody know why this happens? How can I fix it?

I'm using a wireless keyboard and mouse, but they don't have any noticeable lag when typing or moving the cursor. Even the cursor on the in-game menus doesn't have lag.

Turn V-sync off, usually it's the cause.

I'm seeing similar issues. Vsync doesn't do a lot for me. Seems to me:

Triple buffering can really tax some systems and make input unresponsive. I assume the game honors the setting you choose, but definitely try turning that off.

There's a negative mouse acceleration (I personally dislike the feel- like a neck brace or eye surgery). Normally this is subtle but under load or with vsync issues can be really bad.

I think I'm also seeing performance hits related to some visibility/caching system they're using (load a level and spin in a circle). Maybe some related to audio, as they seem to do some processing there.