Episodes with Q are always pretty good, and this is no exception. Seeing Q give his power to one of the Enterprise crew was a great idea.
However, I'm not sure I agree philosophically with the conclusion. I think the notion that "power corrupts" bears some truth but is ultimately a tired cliche that they employ a little too simply in this episode. What is considered power is completely relative. Picard instructs Riker that he should not use his power, that he should continue to use only the abilities he had before. However, if the engines of the Enterprise were improved such that it could reach Warp 12, would Picard refuse to use the advanced speed on the principle that it was too powerful? I also don't believe Riker behaved in character... his reactions to being asked not to use his power aren't consistent with how he normally acts. I also don't really think that having the rest of the crew reject his "gifts" leads to a conclusion that he should abandon his powers. I think, like everything in life, he should have used it as a learning experience, that to have such powers doesn't mean the people around you are willing to have their lives changed even if you think you are helping them. My problem with the way this story resolved is that there actually never were any negative repercussions from any of the times he used his powers, making giving them up a pretty silly decision.
Of course, for story purposes Riker couldn't keep his powers. I think a far better resolution would have been for him to have given in and resurrected the girl that died. And then to go on reviving the life of everyone they encounter who dies, only to realize that he has to alter reality more and more to do so, and that it has unintended consequences for other people he is not aware of. After finding out how his well-intentioned actions cause unintended harm he had not been aware of, he would swear off ever using such powers again, spoiling the plans of Q. I think this would have been a stronger way to tell this story.