Volume on the speaker is pretty good, but this doesn't offer huge sound for its size. The engineers seem to have restrained the top volume a bit because of potential distortion problems at higher volumes, particularly when running a lot of bass through the speaker. An earlier unit I tested had some distortion issues at higher volumes -- it couldn't handle R. Kelly's "My Story" track, for example -- but the final shipping model I tested didn't have this problem (the "My Story" track didn't sound great, but at least it didn't break up).
Still, when you listen to this side-by-side with many other mini Bluetooth speakers, the Oontz is going to come out the clear winner. I liked it's straightforward styling and soft-to-touch finish (it does attract some fingerprints) and despite its simple design it manages to have enough style to avoid looking generic.
Cambridge SoundWorks has also corrected one of the design mistakes it made with the smaller Oontz and Oontz Angle. Those models have a blue light in the middle of the speaker that some users found irritating. The Oontz XL, thankfully, leaves that off. And while a faint light on the Bluetooth button on top of the unit indicates that it is on, all the lighting seems purposely muted to the point where you might not even realize the Oontz is on.
Since this is a larger speaker, it requires an AC adapter for power and doesn't charge with a common Micro-USB charger (like the kind you use for a non-Apple smartphone). It's a little bit of a drawback because you can end up misplacing the AC adapter, but most larger speakers have this requirement.
On the plus side, along with the standard audio input for connecting non-Bluetooth devices, there's a USB port on back that allows you to charge devices such as smartphones. I connected an iPhone 4S and a Samsung Galaxy S4 and they charged fine (the speaker does have to be turned on to charge other devices, but it doesn't have to be plugged into the AC adapter).
Like with virtually all Bluetooth devices, I did get some hiccups in playback (the music cut out from time to time). As I've said in plenty of other reviews, most Bluetooth speakers -- particularly more modestly priced ones -- just don't sound fantastic, so you shouldn't expect the world from the Oontz XL. But comparatively speaking, the Oontz XL does sound good when put up against other speakers in this price range.
Due to its size, the Oontz XL isn't as portable as the mini Bluetooth speakers on the market, which fit more easily in a bag. But the Oontz XL does sound better than those smaller speakers and some larger speakers that cost more (for instance, it sounded better than the $150 Native Union Switch). I preferred the sound of the and UE Boom, but those speakers cost twice as much.
The long and short of it is that this is a good-sounding speaker for its price, and its reasonably attractive design, decent battery, and a couple of extras -- the integrated speakerphone capabilities and the USB charging -- help round out the value equation. At $99.99, I have no problem recommending it, but if the price edges over $125, I'd be a little less enthusiastic about it.