I don't doubt that technology would handle the food issue, but overcrowding is still an issue from a lifestyle standpoint. A "negative" growth rate (say, 1 kid per couple) is not actually negative if no one is dying of old age. If warfare, disease, and famine are the main vectors of population control, I'm not sure it's a happy place.

I'd be really interested in how religion would develop in an immortal society. The removal of guaranteed death, and the diminished precedence of the afterlife, would have a large effect on how religion developed.