Immortality (to aging and disease - I think we can agree that complete physical immortality is impossible) -
ProsDeath will always be an exciting affair
Society can be ruled by extremely wise, spiritually advanced people
Said people increase science output exponentially
Life less 'luck based' - seeing as fairly random hitting problems like cancer are eliminated
Less worrying about death being "just around the corner" - most of the time it will be spontaneous (like being hit by a truck)
Friendships may be strengthened - if, say, immortality of this sort stops aging, and you're able to work for 200+ years, you're going to have some damn close friends. And friends are lovely.
ConsMass starvation causes more death than we would have if we lived 'naturally'
Who's to say people will mature as they age? Maybe we'll all become very cunning materialistic people
Life becomes 'cheap' and mass chaos will take place (this is a risk, not a certainty. However, it's a damn dangerous risk)
If you believe in religion, you're going to spend longer on Earth, which isn't heaven! Also, nasty people avoid hell for longer, which is bad.
Life as a whole loses meaning
People living for 150+ years without proper mental care go insane and must be euthanised for their own good
Overall, I don't really mind - if immortality comes about, cool. If it doesn't... No biggie.
Also, Maggarg - good side of the story. Nice to hear intelligent people's opinions.