[PvK]

Not really, since it makes it easy to get into the habit of relying on a crutch that undermines the gameplay in a subtle but very powerful way, and many players used to lamer games wouldn't learn the intended way to play. When there are many people playing who usually turn back time whenever something bad happens to them, they start giving feedback from their warped perspective, no doubt not admitting how often they use the cheat. Those players will also get less out of the game because they'll find it pretty easy and/or frustrating, likely without understanding why. Etc.

PvK