I disagree. Had Opus#1 and sold it. Lots of firmware quirks, default music player is disaster. Android gives the chance to change one player to another. What you can change in Opus? Nada.
Let me politely disagree here.
Since firmware 2.00 (new UI and better sound signature), Opus #1 is about the best standalone DAP you can get for 300$.
Wonderful signature with VERY large soundstage (even better with balanced output).
Outstanding autonomy even without powering it off, dead easy UI with everything less than 3 clicks away (this is called proper ergonomy, and I'm a professional ergonomy expert), and very few bugs that all have been removed except for the 10s bug, which should be removed with the next firmware and is very minor.
Upon very rare occurence of the music app freezing (usually after week-long hibernation), it restarts in less than 5 seconds without any hassle.
So unless you need network capapibility, it is a great package.
If you have owned Opus #1 before firmware 2.00, I would advise you to stop spreading such a negative feedback, it is clearly not up-to-date.
I don't know what you expected when you bought a DAP without Bluetooth and WiFi and then complain about not being able to switch apps...
I happen to own Opus #1, V10 and V20, and this is one of the only DAP that is worth a place in my bag when I travel, even though V10/V20 are very nice phone/DAPs.