I believe this would depend on the person and their particular need for a smartphone. However, for me, I believe owning a smartphone makes life much easier. I can do so much with my phone, without ever having the need to turn on my computer, watch television, etc.
Smartphones come in extremely handy when traveling, as email, weather, flight schedules, mapping, and a host of other tasks can be performed, without having to lug around a laptop and rely on a WiFi network in a hotel room.
For people who rely solely on public transit, smartphones are almost a necessity, as people check bus and train schedules, the current weather forecast, and use other applications on their smartphones to plan their daily travels.
Although there are times when I think a simple talk-and-text cell phone would be more practical, I then stop and think how much simpler life has become since making the decision to own a smartphone.