Arguably one of the chief things that defines a human being is an awareness and fear of death. It makes us do a lot of stuff. Without that fear, it's really hard for me to say what humanity would do with itself. To be sure, it could barely call itself human anymore.
The average human creates some kind of context for himself that defines his existence. Most people strive to gain a bunch of interesting experiences (travel+fun+etc.), make their mark on society (work+art+etc.), and pass on their genes (family). As far as humanity on the whole goes, our primary concern is survival (which most of contemporary human meaning is probably defined by), the secondary is probably pleasure. In a society of indestructible immortals, I imagine there would only be the wanton seeking out of pleasure and novel experiences, as well as the perhaps unanswerable question of human meaning/consciousness. Is that a bad thing? Kinda hard to say. I guess "bad" and "good" sort of evaporate when you live forever. The fabric of society would probably collapse. If you're immortal, what are consequences? Certainly none that really apply to you. You wouldn't have to listen to anybody.
Try and think, I guess, about what you'd do if you had absolutely no responsibility for anything. After a bunch of naked Everest climbs, maybe diving into the abyss, it all gets kind of boring eventually, I imagine. You'd probably hitch a ride on a space rock with your buddies or something and check out another galaxy, looking for new things, looking for different life, etc. And what if you found stuff? Learn about it, I guess. But it'd all be kind of pointless. It's just novel, interesting.
I dunno. I think, after a while, people would just want to die. After a while I think it would be hard for the majority of immortal humanity to see much point in their existence... unless of course they found some way of "ascending" or etc., via spiritual development or technology or what have you. Perhaps after a certain amount of time humans would be drawn together again in a need to understand the universe/existence (perhaps the final driving force to an immortal) and then work together to research it. If that's even within the realm of comprehension for a human being, I guess we'd figure it out. If not, perhaps a super-intelligent sentient computer would do it for us >_>;
A race of invulnerable supermen is kind of implausible though. Long-lived, disease-immune but still quite fragile humans are much more in the scope of possibility. In that case however, we'd probably overpopulate, and there'd still be war and hunger and all of that business. Even a human who has had his telomeres modified still fears death, and that's incredibly important towards our current habits. A person like that would probably still want all of the same stuff we want today; they'd probably just follow a different, longer routine.
Human meaning is a funny question, though. The universe is this inconceivably large space filled with energy and matter bouncing off/going through/mutating with each other. I think it's kind of silly when people jive on about nature with a capitol N and The Wrath of Mother Earth and how we have this responsibility to it and etc. As mortals we have a responsibility towards maintaining what keeps us alive; which is indeed the earth. But as immortals? Think about it. As we are now, we are an incredibly small, imperfect and arguably cancerous stain covering an equally tiny and, as far as we know, insignificant little planet. Have you ever seen a quasar? What the hell is that? Certainly enough to make me feel like practically nothing. Either we're worthless, or little miracles, or maybe we just -are-. In fact that's probably it. Human meaning is probably simply "existence" or "creation" or something, and finding it out probably won't change anything. The last question for a truly immortal human is probably "What happens when something dies?" Which is something that, tragically, an immortal human would never be able to comprehend.
Well, nevermind. I'm not even going to start tackling that one. Maybe when I'm immortal.
...Or maybe we're all immortal ;O
As far as the main question goes, I guess I'd say "gift." I mean, a lot of people have horrible lives. From a utilitarian standpoint there'd probably be an improvement on the overall happiness scale. We'd also be able to free ourselves (I'm talking about invulnerable immortality) from our insignificant animal bindings and potentially be able to explore the universe, act on it, etc. We'd become "bigger" in a sense. It's a universe of possibility I guess.
If we're talking about "practical" immortality I'd also say gift, at least as far as the individual goes. For society it might become kinda problematic. But as long as you can kill people, there really isn't any problem...
