First of all, I don't think anyone should be nicer or more of an ass to others just for the fact that it would affect their next life. If you try others good or be charitable it should be because you want to, and if you're an ass to others it should because that's your nature. Technically, reincarnation should be "real"...considering that you decompose once you die and organisms eat one another in the food each other and you'll probably end up back in the food of a pregnant woman and part of a baby sooner or later.
As for heaven and hell, some part of me do believe in it. You folks can start saying spaghetti monster and whatever you want. Still, all I'm aiming for is not going to hell if it exists. If I end up stuck on Earth doing the Almighty's dirty work that's still better than hell where the wifi connection is bad and probably no cable television.