I think it would be a nice thing to do for yourself, just to spend some time looking back at your life while you're still here and sort of summing up everything. I think this kind of introspection might give you ideas about what is the "unfinished business" you still have to take care of. Might not be so good for other people who hate reminiscing, though.
As for people reading it once I'm dead...well, there's no way to really tell whether anyone would read it or not and it wouldn't matter to us at that point anyway, so I wouldn't focus on getting anyone else to understand me too much. Maybe just do something like that as an excercise in understanding myself better.