I use a Symfonisk speakers for its Airplay functionality, so that I can play direct from iTunes on my PC to my other Sonos speakers.
It is relatively stable when I play from the PC to the speakers (Play Ones) closest to the PC. However, when I play to more grouped speakers, I get drop outs from speakers randomly and frequently.
I can play from a NAS, hard drive, turntable, CD player, Tunein without any significant issue. But Airplay is a constant issue. I haven't had a single session where it hasn't dropped out.
I live in a small flat/apartment. I've had to overcome poor wifi issues in the past. The block I live in is concrete built so not Sonos'best friend.