I strongly disagree. I bought a discounted iPhone 3 when the 3gs was first released. Within a year my phone was pretty worthless, because the iOS 4 updates made it so interminably slow that I stopped using it as anything other than a dumb phone (which it was never great at anyway). And, of course, I still had a full year left on a two-year contract at that point, so I was not a happy customer. Maybe the situation is better from the 3gs onward, but it sucked for me.
I have to admit that this is true and it was a very disappointing for the user-base to see that their phone got a unacceptable performance after the update.
However Apple learned from it's lessons and the same thing didn't happen with 3 GS and the iPhone 4S.
