I bring a smart phone because it allows quite a bit of simplification. I can leave behind a camera. I can leave behind a book to read in the evenings. Either one of those weigh as much as my phone.

The phone also opens up possibilities on things I can bring without adding weight such as a bird book, tree identification, mushroom id, first aide app, games, mapping, and emergency communication (oops... I came out at the wrong trailhead... where is my car and how do I get to it.) New Iphones are looking at adding satellite communication options. That will be huge.

I still always bring a paper map because the biggest con on a smart phone is keeping it charged. It is hard to estimate battery usage and ensure you always take the appropriate steps to not waste your battery.