Very much the cool new kid on the block, Spotify has taken the market pretty much by storm since its release. While its biggest achievement is probably merely offering some decent competition to Napster, rather than any particular feature, that's not to say that Spotify is any less worthy of recognition.
For a start its desktop application is very slick-looking and comes packed to the gills with features including playlist sharing and social media integration. The catch is, you have to pay for the majority of these.
Spotify offers a free version, Spotify Open, that allows 20 hours of ad-supported listening a month. Persuade an existing user to invite you and you can access Spotify Free and remove that time limit. Stepping up further Spotify Unlimited at £4.99 a month removes the adverts.
At the top of the scale is Spotify Premium at £9.99 and it's here the real fun starts. Only Premium subscribers are permitted access to Spotify's offline mode on both the desktop and mobile clients. Symbian, Android and iPhone apps are available, which makes currently Spotify the leader in that respect.
A particularly useful Spotify feature, especially on lower tiers of the service, is local library integration. Combined with the facility for purchasing songs you fancy keeping from within the program this saves you the hassle of using multiple programs for playing paid-for and free audio.
Plus, Spotify streams in a more advanced audio format - OGG - than other services and offers even higher quality files to its Premium subscribers. Obviously streaming audio isn't exactly CD quality, but these considerations do matter to those of us who still care about the fidelity of the audio we listen to.
While it grabs an unreasonably large amount of public recognition, there are some good reasons why. That it has a free, ad-supported version means you can try before you buy, while the presence of a mobile application for premium subscribers is perfect for those looking to move entirely to streaming/subscription services.