If its properly ventilated, the PS3 has no overheating problems. User error isn't the fault of the manufacturer. About the same for the 360 too actually, only the 360 benefits from having the external power brick, otherwise (judging from the way the fan sounds like a fighter jet powering up while playing a game at room temperature) I GUARANTEE the bitch would be impossible to keep cool.
These consoles put out a shitload of heat, deal with it.
As far as disc scratching, I dont think the PS3's or Wii's drive's mechanisms are even capable of scratching a disk without some type of excess force. The 360, xbox, and ps2 sliding trays are different.