Moving Spotify onto mobile platforms such as the Apple iPhone and Google Android is arguably a make or break move for the makers of this widely acclaimed - but as yet unprofitable - music streaming service.

Spotify on the desktop has attracted a lot of attention and users because unlike other streaming services such as Last.FM it allows you to search for and play specific tracks on demand from a library of over 4 million songs. The service overs a free option where the music is interspersed with 30-second ads and a paid-for, ad-free subscription for £10 a month.

The problem for Spotify is that not enough people have signed up for the subscription service. So now the iPhone and Android apps come into play as they can only be used by paying subscribers. So can the strategy work?

Well untethering Spotify from the desktop PC does undoubtedly make it even more appealing. The mobile app offers the key features of the desktop version - the ability to search and play tracks and to create playlists - and does a good job of replicating the speed and responsiveness that made Spotify so outstanding.

Playlists that are created on the desktop app are automatically transferred to the iPhone - and vice versa. And a key feature of the mobile app is that you can transfer playlists to the iPhone so songs can be played offline when there is no 3G or wi-fi connection available.

Up to 3,333 songs can be stored offline and the sound quality is fine - although not quite as pristine as the the desktop app's high bitrate, 320kb/s streaming.

This offline feature is an absolute lifesave because the app's ability to play music on the move over O2's 3G network is very hit and miss. During peak periods, incessant dropouts can make 3G playback essentially unusable - making you totally reliant on the offline playlists or securing a clear wi-fi signal (Spotify has issues with most office wi-fi networks because it doesn't yet support proxy connections).

Of course, it's a bit harsh to blame the app for O2's failings - but at the moment anyone expecting dropout-free, uninterrupted music playback on the move all the time is going to be disappointed.

Another drawback is that unlike the iPhone's built-in iPod music player, Spotify can't play songs in the background while you do other things on the handset. So if you get an incoming call Spotify will quit and then restart when you hang up - but it won't resume playing the interrupted song. Again, this a limitation created by Apple rather than Spotify, but it is annoying nonetheless.

But despite these issues we still love Spotify for the iPhone. Having access to millions of songs wherever you are is something close to miraculous for most music buffs. Are there enough of them willing to fork out £10 a month for this mobile musical miracle? Only time will tell, but this reviewer has already put his money where his mouth is...