Mikes design look just fine to me, some resistor/caps may need adjusting/adding/removing cant really say how the circuit will perform until its built and tested...just a matter of trying it out really.
The motor driver can be simplified...notice hes using 4 inputs to control the motor. Realistically you will only need 2 inputs...logic 1 on one input and logic 0 on the other cause the motor to rotate. Put logic 0 and logic 1 make the motor turn the other way. Both logic 0 on the inputs stop the motor. Those are the standard control for the H bridge circuit.
As I said earlier on you can use a H bridge IC to simply and to make your design more compact.
If you want you can still use the transistors version :
Notice this only have 2 inputs...this way you can save 2 PICs I/O for other use...either way both design will work. On the 4 input version, you will need to be very careful as not to short circuit the transistors if you coded the PIC wrong...the PIC putting a wrong combination into the transistor can cause them to short each other.
Hope that helps