I just encountered a problem with Microchip's MPLAB X's simulator.
I wrote a very simple piece of program which switches values at the pin PMA0 (which is shared with RB15). The simulator just gave flat low.
I was so puzzled that I connected output pins to a logic analyzer. It showed that I was right and the simulator just didn't work correctly. The logic analyzer also gave me correct output if I set it to be always high or always low.
I am really disappointed about this bug, because it took me and my students hours. Even after I set the output on PMA0 to be constantly high, the virtual logic analyzer still gave me always low.