official site is still "Coming Soon," we can't confirm the stake gun is in the game, and it's tough for us to recommend a download of the new demo.
In the future, we'd recommend that publishers try to tout their best features a bit better. For instance, calling the game "Painkiller: Stake Shooting Challenge" or "Painkiller: Did You See the Way That Stake Killed that Dude?" would not have been inappropriate. So we don't know what to tell you about the demo, but if you want to risk the MBs, go nuts.