Is the 160GB PlayStation 3 backwards compatible?

No it is not Backwards Compatible only the 4 USB port early models were

Due to the availability of an extensive line-up of PS3™ system titles, the 160GB PS3™ system is not backwards compatible with PlayStation®2 titles, but does maintain backwards compatibility for some original PlayStation® titles.

So, As you can see, No compatiblity for any PlayStation 2 games, Only the original PS system. Which is good for me because I don't have any PS2 games, Only the originals! Awesome!