There is a lot of good information here. IMHO, Kitsambler nailed the concise list of "pros."
In my view, it is YOUR Camino. NO one can tell you what is ultimately good, or best for you. It is an individual and private decision.
From my experiences, I finally realized that having one device to replace the weight, and all the charger, adapter, and cable requirements of having to carry as many as FOUR separate devices (SMS phone, digital camera, iPod Touch, and GPS) actually made sense. So, after my last Camino I decided to just hold my nose and dive in. I bought the new iPhone 6s when it came out this past September. It aptly replaces all the forgoing and leaves me with a single charger and cable. I even bought a Euro-style Apple charger in Spain, so I do not need a plug adapter. Every gram counts, eventually.
However, I am still trying to figure out just how to load and use GPS track files in .kml format with Wikiloc.
The GPS track files in .kml and .kms formats are freely available for all Camino routes, at:
http://www.mapacaminosantiago.es/
If anyone here can explain how to load and access the files, I would appreciate it. Yesterday, I got as far as downloading all the .kml files for the Madrid route to Sahagun and the entire
Camino Frances. Both Caminos converge at Sahagun.
Now I am trying to figure out how to manage them on my iPhone and actually use them. My hope is that this capability will replace the need for a hard copy guide book.
All this and, and in consideration of what my colleagues offer above, I submit that the critical factor is that the smart phone not rule your Camino experience. You rule the smart phone...
What I mean is that, during the day, I recommend you turn your cellular / mobile (voice) service off. People cannot easily call you. They can send you text messages, or e-mail. That should do for family emergencies.
However, YOU decide when and where to review those messages each evening at a specific time, and for a limited duration, when you reach your day's destination. So, you set aside the time while you are waiting to have a meal, or reviewing the next day's route to review incoming e-mail and text. As most places you will stop along the Camino will have free Wi-Fi, you can Face Time, Skype, or whatever have you, if you previously agreed you would do this. You can make voice calls over Wi-FI too. Just remember the tie difference between Spain and home...
Before I leave on Camino, I always leave a
communications plan with my family. This way, they know when I will call on a regular schedule. For example, I mUST call my 83-year old mother EVRY SUNDAY at 12:00 here time. In Spain that means I must call at 18:00.
My family and friends also know how to contact me in an emergency. Aside from the regular contact schedule or emergency provisions, no one should be bothering you. Turn your ringer (and vibration) off for the day.
I also send an advance e-mail to all my regular correspondents before I leave, so they will know I am away on another of my Caminos, and not to include me in "shotgun" group e-mail or messaging. Only one-to-one, high value communications are still on order, for the duration.
Lastly, I set up an "out of office" auto-response on my e-mail accounts, So people writing to me are automatically advised NOT to contact me for the specified period of time.
This seems to work for me.
I hope it helps this dialog.