I see you have waited two months since the App was first released to join the community here to report this issue. Did you contact Sonos support in-between and if so, what did they suggest to perhaps fix the issues you mention, or at least what have you tried so far to improve the App connectivity for device discovery/launch time and volume-level adjustment?

Rebooted everything a few times. Deleted the app and reinstalled. Will contact support this week when I have time during their business hours 

Ah okay… hope you can get it sorted.