I'm not exceptionally well versed on Hinduism, but I really don't like the cast system (ie the untouchables) where you're supposed to look down your nose and not help the disadvantaged because it's just karma punishing them for evil deeds in their past lives. I think this is one of the big reasons the Sikh (sp?) religion was develped. they have this thing where food is sacred and they're not supposed to turn down any hungry person for a meal.

personally, I like the buddhist concept of karma a lot more because it's not some universal judge that punishes and rewards people. Rather, it believes the state of mind a person dies with determines the karma that will be passed on to the next life. a person who is evil and negative will influence the next life as such, and a person pure of mind, peacefull, and good willed will influence the next life in such a possitive way.
I use the term "the next life" instead of "your next life" because there's a common misconception towards buddhism that "you" are reborn when in fact there is no permanent self. the whole deal is that the essence or your consciousness joins and influences the consciousness of the next person born to create the new human being.
now there are theories about coming back as different species, or in different realms of existence, but this is more from taoist and confucianist influence combined with buddhism in cultures that had these 2 as their prior religions. well, except the coming back as different species thing, that's debated amount different buddhist sects, and who really knows.