Cool. I don't know. I have an old Wacom Bluetooth tablet, and it had a noticeable lag, but it was also quite old.

The lag -even milliseconds- can be enough to ruin the experience for an artist. The iPad/pen lag is not noticeable. That said, I think the graphics app probably has more to do with it, than the hardware.

I think "faceless" wired Wacom tablets had no noticeable lag at all (we had a couple, at my old job). I have never used one of their Cintiq tablets, though.