I'm not arguing either, and I will concede that a non-removable battery isn't my preferred approach. My belief is that while long run times are certainly awesome, and if the Onkyo had more I wouldn't complain, but really it is quite easy to charge your device. I'm sure some people like to have music on constantly, but for me and I'm sure quite a few others, plugging in your device while you sleep isn't really being tethered that restrictively.
There will never be a day in my life that I could, or would want to listen to 8 hours of music so long battery life is a feature that I won't realistically need. Will it kick me in the ass from time to time when I forget to charge at night and start my commute with low battery? Sure, but that won't ruin my day. More disappointing to me would be using a DAP with quiet mastered music and finding that it can't drive my headphones to a volume level I prefer. I had that with the A17, tried some 80s and 70s masters and just forget it in terms of volume with even my MDR 1A, just too darn quiet and uninvolving.
As for the Sony UI, I was actually complimenting it. I had an A17 not long back and I loved how easy it was to use. I think Sony has the UI thing pretty dialed in and if the Onkyo gets close I will be happy as I really am not a power user. I listen to albums and playlists I make up so basic functionality will do.