NOTE ADDED 7th SEPTEMBER - SONOS HAS NOW FIXED THIS, SEE THIS STORY
While Sonos owners will be celebrating the arrival of the compact Play:3, those using their Sonos systems with a Mac-based music library should hold back on updating to Apple's new Lion operating system.
"The new Mac OS X 10.7 (Lion) release is not compatible with your current Sonos system if your Music Library is stored on your Mac," warns an email the company has despatched to those who have registered their systems as operating with a Mac-based version of the Sonos Controller.
The company promises a fix in two to four weeks, and has detailed the issues involved here http://forums.sonos.com/showthread.php?t=23442 , which include some apparently alarming changes to OS X's handling of NTFS-formatted drives, which could have ramifications far beyond the issues with Sonos libraries.
Customers with concerns should contact their Sonos dealer or deal direct with the company's tech support.
More information: Sonos