The downside to immortality is that the wealthy would just keep getting wealthier (since building wealth is at least partly a function of having wealth and having experience accumulating wealth) until eventually they are more important than governments. And the great War of 2188 will be of the nation of Zuckerberg vs the nation of the United States of Buffett, winner gets Earth, loser is expelled to roam space for all time.
Ok, I should drink less coffee. :)