To my way of thinking, the ideal user of this product will be someone who has a notebook/laptop that doesn't offer exceptional onboard audio output. If you're looking for a product that will give you better-sounding audio without having to drag speakers around or spend a small fortune, this is for you.
How easy is it to use? Very. It connects to the computer via a small USB receiver, which quickly installs itself- no driver issues or incompatibility messages. Once it installs itself, it works flawlessly. The Bluetooth works equally well- pairing is simple, so you can use it with Bluetooth-capable phones and media players.
How durable and reliable is it? Very. The battery life is robust- about ten hours between charges. It's well-built, plastic, but a nice heft to it without it being heavy. A carry-case is provided, and the carry-case includes space for the charger/AC adapter. The USB receiver hides invisibly in the back of the unit when not in use.
Why not five stars, then? Well, the proof of audio gear is in the playing, and that's where the Z515 comes up just a bit short. The performance isn't BAD by any means, but because both stereo speakers are (obviously) co-located, it ends up sounding a bit canned. To be fair, it doesn't sound any worse than standard laptop audio, but it really doesn't sound significantly BETTER, either (though it is louder than most of the machines I tested it with). Because of the lack of stereo separation, the audio playback doesn't really come across as significantly high-grade. I think the reason for this is that most people, when using a laptop, sit directly in front of it, and if the laptop has stereo speakers (which most do now, even if they're humble and unspectacular), then users get that ever-so-subtle yet ever-so-effective stereo effect. I don't know if most people will sit with the Z515 directly in front of them, and if they don't, they lose that subtle experience of stereo separation. It's not a BAD thing- it's just the inevitable result of having both sides of the stereo be so close together.
In summary, this isn't a BAD product- in fact, it's a solid product that totally delivers from the technical aspect, and that does precisely what its manufacturer says it will-, but potential buyers DO need to consider what they will expect the audio to sound like coming out of it. This isn't a home-stereo replacement, but if what you need is flexibility in where the audio in your computer or mobile device will go, the Z515 will get the job done.