With these types of Bluetooth mini speakers, good sound is a relative term. Overall, they just don't sound great, they offer virtually no stereo separation, and they have their limitations as far as clarity and bass performance go. All that said, relatively speaking, the Oontz sounds good for its modest price point and size. It plays fairly loud, has a reasonable amount of detail, and gives enough bass so that it doesn't sound totally thin. Like most of these speakers, it's strongest in the midrange, so it will sound best with lighter fare (less bass-heavy music) and acoustic tracks.
It sounds similar to such speakers as the $99.99 UE Mobile Boombox, but costs half as much (though the pricier UE Mobile Boombox is a sturdier unit with a slicker look). In terms of sound, I also think the Oontz is a notch up from the $49.99 Philips SoundShooter, one of our favorite tiny speakers. However, it doesn't sound as good or play quite as loud as the $99 JBL Flip, though the Oontz does offer better battery life.
Comparing it with the lower-priced Oontz Angle, the Oontz does offer bigger bass and overall fuller sound. It's not a huge difference, but it is noticeable. In some ways that's a shame because I like the design of the Oontz Angle a bit better.
It is worth noting that you will get some distortion with this speaker (and the Oontz Angle) at higher volumes and while the speaker does have rubber feet, it may move around a bit on smooth surfaces if you play tunes with heavier bass lines at high volumes.
As noted, battery life is good. I exceeded the 10 hours of rated battery life in my tests, though I played my music at more moderate levels.
While I expect to see more quality mini speakers in this price range in the future, for now the Oontz is one of the better-sounding mini speakers at the $50 price point and it also offers strong battery life and speakerphone capabilities.
I did have a few gripes (Mini-USB port, bright blue light on front, no dedicated source switch), but overall I think it's a good value. It may not quite be a steal, but it does offer a good amount of bang for the buck, and if you value sound quality over design, I think it's worth paying the extra $10 to get this model instead of the Oontz Angle.