Even if their own software is Windows only, if it's a bog-standard DVB-T receiver, which is what it looks like, you still might be use it with different software, like this bloke's doing with a Freecom stick, for example. If you already own a laptop and have a spare tenner, it might well be worth a punt.
Basically though, if it's what I think it is, if you're using it in the UK, it'll be a Freeview receiver on a USB stick – pretty cool and great for a tenner, but not some magical free gateway to the television and radio stations of the world. If you take your laptop on holiday, I'm pretty sure you'd only see what's available free to air locally, and then only if it's a country using the DVB-T standard (which, to be fair, includes all of Europe). As for their claim of 5,000-plus TV channels and 20,000 radio stations – well, if you add together everything available everywhere, then maybe, but you'd only be able to access to whatever's available locally at any one time.
If you're stuck for ideas for things to listen to on Spotify, then you'd be better off subscribing to a few playlist feeds, I'd reckon.