£10 a month
Which gets you:
-Unlimited Streaming at 320kbps Vorbis
-No ads
-Over 10 million tracks
-Online and offline
On:
Windows (XP, Vista, 7)
Mac OS X (10.4, 10.5, 10.6 including PowerPC)
Linux (Debian/Ubuntu or Wine)
iOS
Android
Symbian
Windows Mobile
You can use any number of the above clients (I use it with 6 devices on a regular basis). When I make a change to my playlists, that happens on the other computers/devices instantly.