I guess it may depend on the internet connection. It works and plays okay here. (iPad Safari Browser).

Yup freaking slow and sucks on mobile. Let’s hope they did a better job with the security that exposes our speakers to the Internet than they’ve done with the app. 

Huh? …Sonos products have always been available in some shape, or form, to the internet - it’s why we are able to stream to them from online services, or use SMAPI based Apps etc. I don’t personally see the Web App as being any less secure - it needs a users Sonos account credentials to gain access. Just use a strong Sonos account password and perhaps change it from time to time and don’t share it with others. 

The difference here compared to say streaming a song is the remote access/control of your system and potential for your network to be compromised with only user/password. There is no 2fa/mfa option which is the minimum security expected, no option to disable this entirely (why must you have it on if you won’t use it?) or even warning to customers that this is happening. 
 

I don’t expect most people to care about this, but it is a legitimate concern compounded by the fact that every thing about the app is a buggy mess.