Overcrowding is not a problem - it's a big universe. Our species has already (decades ago) traveled from this planet to our moon and returned safely. It can't be too far in the future when we will be able to travel farther and establish independent communities elsewhere. Meanwhile, advancing technologies will extend the carrying capacity of the earth, which hasn't even been reached yet under current technologies.

People who say they don't want to live forever are probably assuming that it would bring ever declining health, as is the case with aging today. Ray Kurzweil claims that the immortality we are very near achieving will include the ability to dial our physical condition back to that of a healthy young adult and keep it that way indefinitely.

If the technology became available, reliable and safe, choosing not to take advantage of it would be the equivalent of suicide. Why would any reasonable 85 year old who has the health of a 25 year old choose to die at that particular age instead of ten years sooner or ten years later? Don't say, "Because it's what nature (or God) intended", because we're long past that point already; without the human interventions of medicine, housing, agriculture, etc. we'd all still be dying before 35 or 40, the way nature originally intended. We have never refused age extension technologies before, and I doubt we will going forward.

The issue of it being an evolution-stopper is an interesting point, but we have clearly already started influencing the path of our own evolution and with advances in genetic science, etc. the very mechanisms of evolution will transfer into our own hands. It's not unreasonable to think that at some point "evolutionary" adjustments can be made to existing individuals.

When your grandparents were children no one could imagine a time when an ordinary nine year old might carry a pocket sized computer thousands of times more powerful than the one used to fly that first man to the moon. Such a time has arrived. Advances will be coming at us faster every day. Buckle your seatbelt and prepare your mind.