Resteeming can make a difference, mostly for the original poster. A resteem reaches a new (at least partly) group of followers, so the post is wider and longer visible. For the resteemer it gains not all that much, from my experience.
I dont mind if people resteem, if its done from honest interest. Only if I see people who resteem lots of high upvote posts, because they think they can participate on the high payout, I find it a little cheap.