The latest version 2.0 of Jambox software provides a silent mode which mutes the sound effects for startup, shutdown, pairing, etc. Unfortunately this is not documented even in the latest manual. This became available roughly April 2013.
To activate silent mode, hold down the Talk and Minus button while powering it on. The sound effects will stay off until you hold down Talk and Plus buttons while powering on.
Before silent mode was available it was difficult to use this device in a public situation as the sound effects would periodically happen (apparently responding to Bluetooth operations from mobile devices in the audience). It could also not be discreetly powered on and off. It was a mistake to ship the device without that functionality, however it's water under the bridge and it works OK now.
Another design shortcoming which is a constant, persistent irritant to customers is failure to use a standard micro USB connector. The USB cable is needed for programming the speaker behavior, such as voice caller ID, voice announcements of battery life & pairing status, etc.
Designers of ultra-miniaturized devices can at least argue the fractional millimeter saved is worthwhile. By contrast the Big Jambox is a full size device and there is no space issue. If you lose the proprietary USB cable, you can't program the device. This problem is not unique to Big Jambox, it is so common the EU has passed legislation to outlaw proprietary USB charging connectors on mobile devices.
Besides these two self-inflicted and unnecessary design mistakes, the audio quality is pretty good, max volume available is good, form factor is good, Bluetooth connection speed and reliability seems good.