Jay,
May I ask what modifications you did to yours? I also am not happy with the transistor or the op amp solution... Mine is complete except for the Target MCLR circuitry and I also installed a 78M08 regulator for generating the 13v VPP voltage...
Just hooked mine up to MPLAB for the first time a few minutes ago and successfully downloaded an OS and can read the ADC's in the Programmer>Status window... But it obviously faults with "no target device" and no voltages detected on the Target MCLR ADC resistors...
Regards, Mike
<added>
Sorry, I should have mentioned mine is RS-232 not USB...