I have a copy and I have to say it is quite magical. Both the audio and the visuals are mesmerizing. Note this is not a synthesizer. Ambient tracks play in the background as you propel your "mote" through various levels. This is one beautifully addictive game. If you have an iPad, this is a no brainer, just get it.
iPads on Ebay
Update: If you do not have or plan to get an iPad you can find Osmos for the PC, Mac and Linux here. I should also note Mat Jarvis, one of the people behind Osmos also brought us Gas 0095 featured in a number of posts here.