i don't actually own one of these, but at school pretty much every music lesson is spent sitting at one and playing instead of working, so i think i'm qualified enough to be talking about them. the pss460 is fantastic - good presets [with stereo symphonic sound!] especially the electric piano... mmm...
it's very easy to use and the synthesis is controlled by six sliders controling 'wave', 'spectrum', attack, decay, volume and one more which escapes me at the moment. best sounds are fat decaying bass monsters. crazy effects can be acheived by moving the sliders whilst holding down the keys.
if you see this keyboard for less than £60 buy it. and sell it to me.