These tiny Bluetooth speakers do have their sound limitations, so you shouldn't expect the world from them, particularly in the bass department (it's going to sound restrained with techno and hip-hop, for instance).
That said, I though the BT2500B managed to avoid sounding harsh and was relatively distortion-free, though it performs better at more modest volume levels and with less complicated music where you don't have a bunch of instruments playing all at once. It's designed for casual, not critical listening, and would also work well as an audio source for movies on a tablet or laptop.
It also performed fairly well as a speakerphone as long as I didn't wander too far away from the speaker's microphone while talking.
In terms of similar products I've reviewed, I'd say this is closest to the hockey-puck-size JBL Micro Wireless ($49.99), which a lot of people like. This Philips measures up well in terms of sound and adds the speakerphone capabilities, a nice plus. It's also comparable to the new Divoom Voombox Travel (also $49.99), which delivers similar sound but adds a "ruggedized" splash-proof body to the mix. Indeed, the rough-and-tumble Divoom looked a bit more durable than the Philips.
The BT2500 charges via Micro-USB and its battery life is rated at 5 hours (the BT3500 and JBL Micro Wireless are also rated at 5 hours, the Divoom at 6). You'd ideally like to have a speaker rated for at least 8 hours of listening, but if you don't crank the volume too much, you may be able to improve on that 5-hour number.
Mini Bluetooth speakers are a dime a dozen these days but some, including the Philips BT2500B, are better than others.
Its slim shape and compact footprint make it ideal for travel, and while it does have its sound limitations, its output is fairly impressive for its small size. No, it's not as swanky or sturdily built as the Jawbone Mini Jambox, but it costs a lot less, making it a good value choice in the mini Bluetooth speaker category.