Design and form factor
The UE Mobile Boombox sounds very good for its size and price. I've used both cheaper Bluetooth speakers (the HMDX Jam) and more expensive ones (including UE's full-size Boombox), and the Mobile Boombox strikes a very good balance of value and quality. It gets reasonably loud for a small speaker, has very little distortion at most typical listening volumes, and pairs easily with most tablets and smartphones. Battery life is good, and it uses a standard micro-USB port for charging. If you're looking for a good Bluetooth speaker for under $100, it's definitely worth considering.