1) What is the value of getting a tablet with or without cellular service to use with the Phantom 4?
2) I also read that T-Mobile offers free cellular service for up to 200 MB? What amount of cellular data is used when flying? I can't seem to find the link.
3) If you have a non-cellular tablet what features are missing if any when using the Phantom 4?
4) Also if you have a tablet without cellular can you instead just tether to your smartphone to use your cellular and GPS service?  
5) And how is GPS used with the Phantom 4?

You don't need cellular, P4 operates from DJI go app , you may need for maps but you can set tablet as hotspot from your phone you will then have maps as well, no data is used flying P4.gps is used as a positioning module, you can read all all about this in the manual.

The only features you will be missing is follow me and loading maps when you get to your flying area.
But you can cache the map for your flying area at home or use your cell phone as a hotspot and get the map data.
You can try to use follow me with your phone as a hotspot and it may or may not work. It hasn't worked for me but some claim that it worked.

DJI-Ken Posted at 2016-7-12 13:35
The only features you will be missing is follow me and loading maps when you get to your flying area ...

Since I'm awaiting my P4 but trying to buy a tablet I have no hands on experience.

How are maps used with the P4? And to use the maps I'll first need to load the area where I'll be flying before I get there using WiFi?

RE follow me feature, I assume that it requires GPS accuracy but specifically with Cellular not with Wifi?

amh2007@nyu.edu Posted at 2016-7-13 03:11
Since I'm awaiting my P4 but trying to buy a tablet I have no hands on experience.

How are maps  ...

You can download the GO app and you can see the map page to see how it look.
On IOS in the General Settings there's an option to "Cache Map in Background" and it automatically saves the current map you are viewing in the app.
Yes, follow me requires GPS from the mobile device or a teathered bluetooth GPS.

DJI-Ken Posted at 2016-7-12 15:34
You can download the GO app and you can see the map page to see how it look.
On IOS in the General ...

How do you cache maps on an Android device?
Thanks,
Marty

mmarkoe Posted at 2016-7-13 05:26
How do you cache maps on an Android device?
Thanks,
Marty

It does it automatically. At home and on WiFi, pull up the map and scroll to wherever you are going to fly and zoom in some and you'll get more detailed of the map.
Then go to your field and the map will be there when you startup the app.

Just to add...  If you're considering an Apple tablet... For some reason Apple tablets without cellular capability don't have GPS receivers.   GPS in the tablet allows you to see your position on the map as well as the P4's.

It's  not necessary to have cellular service on your tablet, especially so considering you need a new data plan for the tablet itself.
It would be better if you use the extra money to buy a GPS tracker or an extra battery.