I have to away from my S4 for one week and has been using a feature phone 4 days.Things I really missed:
My most is GPS/Maps. Even not for travelling, a daily route I frequently have google tell me exact times and routes for transit than remember it or figure it out. I turn on Gps often and battery drains fast so I also missed my beast mpj extended battery. I also tend to not know where streets are in relation to each other so just Map everything. Other than those, killing time with ebooks, and occasionally texting or calling people.
Well I'm pretty much on Ingress whenever I leave the house, as I'm in competition with other players in my local area over a group of portals. So I need to stock up enough resources as I leave the house, before I am able to plan my next attack.
I also suggest you play Ingress, it is based off Google Maps, so you will be able to find your way in different areas, as well as play against the enemies for supremacy over portals and control fields in different areas, which is also tons of fun. It's awesome for killing time if you are bored on public transport or as a passenger in a car. This game allows you to strategise and even met new people if you wish. Anyway the choice is your's but if you do plan on playing, make sure you join the Resistance.
The thing I use most frequently is the included Google Now service or Google Search. They are pretty much the same thing. The thing that I use for the greatest duration is split between Zite and 9Gag. It's really useful to have groundbreaking news stories from a variety of resources about things that interest you. It allows you to speak on a great many topics that you enjoy.
I have literally sent/received maybe 10 text messages in the last three weeks (all of those were family), I've talked on the phone once since probably January or so, and I've used about a gigabyte of data since last June. I have a whopping 10 apps installed.