Venetian/Palazzo have completely ended comps except for the really top players. More info here.

MGM has just rolled out a new comp program (Mlife). I don't think there's enough known about it yet to see how good it will be. From what I've read, the biggest "advantage" they are promoting is that it's more of a self-serve program. I see that they still don't allow people to book some offers online though (which is really silly).

Caesar's/Harrah's total rewards is still offering comps to me (at IP/Harrah's/Flamingo, not Caesar's or PH), with very little play in their casinos. From reading other boards, it appears that nothing has changed here recently regarding how they hand out comps.