YONO is pretty bad and I used them too because SBI as my first bank account like most of the Indian residents and 6/10 times the payments will be failed due to server error and for a government bank with such large userbase not given proper resource like HDFC or ICICI do.
As far as information from SBI employees go, they paid a lot of money to TCS to develop this app and look at what sort of a app they ended up with. From the outside it looks good but inside its buggy and not adopted to modern smartphones. Often goes on maintenance over weekends and server crashes are nothing new.Quote
But for the record it is the official erupee wallet app from SBI. 
I will wait before starting that journey. If I dont find any use of that system why will I install it. They need to convince me to use it not the other way round.