What I hate more is the thought of having my financial data stored in some shady, cobbled together, cloud service, hosted somewhere on Amazon AWS.
I predict, that it is only a question of time until they will encounter some disastrous data leak.
Begin a YNAB user for more than a year now, I am really angry at them for this move. So I'll guess I have to move on to something else after the support for the YNAB4 apps will be shut down.
To power this with a battery a better solution would be to use a switching power supply. (For example a LTC3525 step up converter with two AA 1.5 V batteries.)
The linear voltage regulator basically turns 4V of the 9V block into heat. This is not really efficient.