Personally I feel that I along with everyone else have every right to take a life if I so determine to.
The fact that I don't is simply because I don't act in futility. In my mind I have determined that unless my life or those that I determine to be close to me(freinds, relatives, loved ones) is threatened then I simply won't take a life, not that it is the right or wrong thing to do.
Both the mind power and the life boat case I would have no difficulty with any moral dilema about taking lives.
In the mind power case taking a life for the "greater good" is based on the idea that you know what the better cause is and is more or less determined by location. Most people believe that they would be in the "right" because of how they were raised. Me though? probably wouldn't use it but keep it anyway for the "just in case" moment where my survival would depend on it.
In the lifeboat case it is simply a matter of survival and based on that I would kick everyone off to insure my own survival, that is of course the whole point of life isn't it to survive and pass on your genes.