I believe it. Like MinX said, our experiences - good or bad - are the results of previous actions (or inaction). One way or the other, we all get what's coming to us, in this life or the next.
My faith in this concept was actually reaffirmed some months back when a local politician/official who'd given a relation of mine (and others in the town) a hard time was forced to resign because of a highly publicized corruption scandal. What goes around, definitely comes around...in this case, "it" came back with some really sharp teeth. ;)