It would work out that way in case I'd just want to use the phone for email/sms/mms/internet/calendar. But communicating with friends needs me to get whatsapp - or a better alternative they can run on their iOS/Android Phones.
Some apps are too useful to pass like the from the "Deutsche Bahn" for trains schedule and tickets directly sent to the phone.
Yes, those "needed" apps are limited but very useful. Just in this case I don't need to print out the ticket but can get it while on the run.
Looking up train schedules on the internet takes way more time (at least it did on my n900) than it does in the app.

Refectory plan apps are available too, easy access to university internal stuff, For other things I need to learn QT/C++ myself I fear.

At this point Firefox as browser is also needed (for me) the native Sailfish browser (locked in google search!) doesn't do it plus a music player.

Would you suggest me to keep the Jolla Phone then instead of working my way through the rooted Android jungle?