Using the GND and VCC Pins

Are the two GND and the two VCC pins connected internally (on the ATmega 168) in a way which allows you to connect different parts of a circuit to the different pins without bridging them.

I wonder as i am building a PCB which would be much easier if this true!

They are probably connected internally, but you should always wire them both up in your circuit. The manufacturers wouldn't have used up extra pins if they didn't need to! If you only wire up one of the two Vcc or Gnd pins, you will most likely have a very unreliable Arduino. Remember to fit all the decoupling capacitors, too!