Like those other mini speakers I mentioned, this model plays pretty loud for its size. While none of these mini speakers delivers really good sound, I felt the Logitech Mini Boom Box and AT&T Logitech Speak'r were a step up in terms of sound quality. They offer a little more bass and detail. Again, all these speakers have their limitations and most just can't handle heavy bass at higher volumes, including the SPX15.
Unsurprisingly, where this speaker sounded best was on acoustic material and lighter fare. For example, the live acoustic version of Adele's "Turning Tables" sounded just fine and made me think I was listening to a larger speaker. I also found that it worked well enough as a speakerphone, though you'll want to keep the unit within a few feet of you when talking into the integrated microphone (Bluetooth speakers generally allow you to stream sound from a device up to 30 feet away).
The truth is I'd have no problem recommending this Rocketfish if it were cheaper. I understand there are certain costs involved when you include a lithium ion rechargeable battery (these types of batteries are fairly expensive), but the SPX15 just doesn't feel like it should cost $99 ($69 or $79 max would make it a more attractive buy).