I think it's amazing how many older iPhones you see out in the public. Go to the mall and you'll still see a bunch of iphone 4's and an occasional 3GS.
That is high praise for Apple that they have so many devices still in use. It speaks to the quality and durability of the iphone. And as much as we complain about the older phones, the fact that so many are still out in the wild does mean that people still enjoy them. If they didn't, they'd move on to another phone.