My Tivo is connected via my AV receiver with the AV sync option permanently set to +200ms to overcome the lip sync issue. Every time I restart the Tivo the lip sync corrects itself (so my +200ms offset doesn't need to be applied), but only for about an hour or two before it drifts out again.
I didn't even bother reporting it. A quick Google search when I first noticed it made me realise it's a common problem and so I've just learned to live with it. VM probably love customers like me (the lazy ones).