So it's been over 250 miles now and the shifting is still the same. Torque converter doesn't seem to be locking up.
I did some searching on what might cause it, and a few pages talked about how torque converter lockup is for fuel economy and drivetrain efficiency, and the loss of lock up is usually from the computer having whatever code erased or a chip removed. One page did mention that the MAF sensor sometimes causes it to sense load improperly (MAF cleaner still not arrived yet :/)
Also saw this TSB about ECU damage:
Tsb: All nissan models; ecu damage can result from improper battery connection
And I'm thinking I may have done something wrong while disconnecting the battery to reset the ecu.
I'm still hoping that it is indeed due to dirty MAF sensors though. It'd be much much easier than taking it to the dealership.